SurveyUtil

Complexity

Total Complexity

470

Size/Duplication

Total Lines	3637
Duplicated Lines	0 %

Importance

Changes

0

48 Methods

Rating	Name	Duplication	Size	Complexity
F	display_user_report()	0	171	21
B	isSurveyAnsweredFlagged()	0	22	5
A	invitationExists()	0	18	1
F	make_field_list()	0	142	27
B	display_survey_list_for_coach()	0	42	3
F	display_complete_report()	0	236	48
F	saveInvitations()	0	117	23
A	get_answers_of_question_by_user()	0	22	3
F	handle_reporting_actions()	0	34	11
F	display_comparative_report()	0	236	32
C	export_complete_report_row()	0	73	18
B	drawChart()	0	59	7
F	display_question_report()	0	223	34
A	get_number_of_survey_invitations()	0	17	1
B	store_answer()	0	44	4
D	display_question_report_score()	0	97	10
B	save_invitation()	0	20	6
C	comparative_check()	0	35	8
A	checkIfSurveyHasAnswers()	0	19	3
D	get_survey_data()	0	120	9
A	show_link_available()	0	51	3
A	modify_filter_for_coach()	0	13	1
B	send_invitation_mail()	0	62	5
B	displaySurveyListForDrh()	0	35	2
F	export_complete_report_xls()	0	214	31
A	checkHideEditionToolsByCode()	0	17	4
A	get_number_of_surveys()	0	17	2
C	get_survey_data_for_coach()	0	70	7
B	get_survey_invitations_data()	0	26	2
A	save_invite_mail()	0	18	2
C	getSurveyList()	0	113	11
B	delete_user_report()	0	35	4
A	remove_answer()	0	12	1
C	get_invited_users()	0	63	12
A	anonymous_filter()	0	6	2
B	display_survey_list()	0	43	4
C	check_first_last_question()	0	29	8
A	display_survey_search_form()	0	11	1
C	check_parameters()	0	61	15
F	export_complete_report()	0	171	24
A	flagSurveyAsAnswered()	0	10	2
A	get_number_of_surveys_for_coach()	0	5	1
C	display_complete_report_row()	0	72	14
A	get_invitations()	0	19	2
B	survey_search_restriction()	0	18	6
C	modify_filter()	0	75	11
C	export_complete_report_row_xls()	0	66	16
B	update_count_invited()	0	34	3

<?php
/* For licensing terms, see /license.txt */

use Chamilo\CourseBundle\Entity\CSurvey;
use ChamiloSession as Session;

/**
 * This class offers a series of general utility functions for survey querying and display
 * @package chamilo.survey
 */
class SurveyUtil
{
    /**
     * Checks whether the given survey has a pagebreak question as the first
     * or the last question.
     * If so, break the current process, displaying an error message
     * @param    integer $survey_id Survey ID (database ID)
     * @param    boolean $continue Optional. Whether to continue the current
     * process or exit when breaking condition found. Defaults to true (do not break).
     * @return    void
     */
    public static function check_first_last_question($survey_id, $continue = true)
    {
        // Table definitions
        $tbl_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $course_id = api_get_course_int_id();

        // Getting the information of the question
        $sql = "SELECT * FROM $tbl_survey_question
                WHERE c_id = $course_id AND survey_id='".Database::escape_string($survey_id)."'
                ORDER BY sort ASC";
        $result = Database::query($sql);
        $total = Database::num_rows($result);
        $counter = 1;
        $error = false;
        while ($row = Database::fetch_array($result, 'ASSOC')) {
            if ($counter == 1 && $row['type'] == 'pagebreak') {
                echo Display::return_message(get_lang('PagebreakNotFirst'), 'error', false);
                $error = true;
            }
            if ($counter == $total && $row['type'] == 'pagebreak') {
                echo Display::return_message(get_lang('PagebreakNotLast'), 'error', false);
                $error = true;
            }
            $counter++;
        }

        if (!$continue && $error) {
            Display::display_footer();
            exit;

Using exit here is not recommended.

        }
    }

    /**
     * This function removes an (or multiple) answer(s) of a user on a question of a survey
     *
     * @param mixed   The user id or email of the person who fills the survey
     * @param integer The survey id
     * @param integer The question id
     * @param integer The option id
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function remove_answer($user, $survey_id, $question_id, $course_id)
    {
        $course_id = intval($course_id);
        // table definition
        $table = Database::get_course_table(TABLE_SURVEY_ANSWER);
        $sql = "DELETE FROM $table
				WHERE
				    c_id = $course_id AND
                    user = '".Database::escape_string($user)."' AND
                    survey_id = '".intval($survey_id)."' AND
                    question_id = '".intval($question_id)."'";
        Database::query($sql);
    }

    /**
     * This function stores an answer of a user on a question of a survey
     *
     * @param mixed   The user id or email of the person who fills the survey
     * @param integer Survey id
     * @param integer Question id
     * @param integer Option id
     * @param string  Option value
     * @param array $survey_data Survey data settings
     * @return bool False if insufficient data, true otherwise
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function store_answer(
        $user,
        $survey_id,
        $question_id,
        $option_id,
        $option_value,
        $survey_data
    ) {
        // If the question_id is empty, don't store an answer
        if (empty($question_id)) {
            return false;
        }
        // Table definition
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);

        // Make the survey anonymous
        if ($survey_data['anonymous'] == 1) {
            $surveyUser = Session::read('surveyuser');
            if (empty($surveyUser)) {
                $user = md5($user.time());
                Session::write('surveyuser', $user);
            } else {
                $user = Session::read('surveyuser');
            }
        }

        $course_id = $survey_data['c_id'];

        $sql = "INSERT INTO $table_survey_answer (c_id, user, survey_id, question_id, option_id, value) VALUES (
				$course_id,
				'".Database::escape_string($user)."',
				'".Database::escape_string($survey_id)."',
				'".Database::escape_string($question_id)."',
				'".Database::escape_string($option_id)."',
				'".Database::escape_string($option_value)."'
				)";
        Database::query($sql);
        $insertId = Database::insert_id();

        $sql = "UPDATE $table_survey_answer SET answer_id = $insertId 
                WHERE iid = $insertId";
        Database::query($sql);

        return true;
    }

    /**
     * This function checks the parameters that are used in this page
     *
     * @return string $people_filled The header, an error and the footer if any parameter fails, else it returns true
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007
     */
    public static function check_parameters($people_filled)
    {
        $error = false;

        // Getting the survey data
        $survey_data = SurveyManager::get_survey($_GET['survey_id']);

        // $_GET['survey_id'] has to be numeric
        if (!is_numeric($_GET['survey_id'])) {
            $error = get_lang('IllegalSurveyId');
        }

        // $_GET['action']
        $allowed_actions = array(
            'overview',
            'questionreport',
            'userreport',
            'comparativereport',
            'completereport',
            'deleteuserreport'
        );
        if (isset($_GET['action']) && !in_array($_GET['action'], $allowed_actions)) {
            $error = get_lang('ActionNotAllowed');
        }

        // User report
        if (isset($_GET['action']) && $_GET['action'] == 'userreport') {
            if ($survey_data['anonymous'] == 0) {
                foreach ($people_filled as $key => & $value) {
                    $people_filled_userids[] = $value['invited_user'];
                }
            } else {
                $people_filled_userids = $people_filled;
            }

            if (isset($_GET['user']) && !in_array($_GET['user'], $people_filled_userids)) {

The variable $people_filled_userids does not seem to be defined for all execution paths leading up to this point.

                $error = get_lang('UnknowUser');
            }
        }

        // Question report
        if (isset($_GET['action']) && $_GET['action'] == 'questionreport') {
            if (isset($_GET['question']) && !is_numeric($_GET['question'])) {
                $error = get_lang('UnknowQuestion');
            }
        }

        if ($error) {

The expression $error of type false|string is loosely compared to true; this is ambiguous if the string can be empty. You might want to explicitly use !== false instead.

            $tool_name = get_lang('Reporting');
            Display::addFlash(
                Display::return_message(
                    get_lang('Error').': '.$error,
                    'error',
                    false
                )
            );
            Display::display_header($tool_name);
            Display::display_footer();
            exit;

Using exit here is not recommended.

        } else {
            return true;

The expression return true returns the type true which is incompatible with the documented return type string.

        }
    }

    /**
     * This function deals with the action handling
     * @param array $survey_data
     * @param array $people_filled
     * @return void
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007
     */
    public static function handle_reporting_actions($survey_data, $people_filled)
    {
        $action = isset($_GET['action']) ? $_GET['action'] : null;

        // Getting the number of question
        $temp_questions_data = SurveyManager::get_questions($_GET['survey_id']);

        // Sorting like they should be displayed and removing the non-answer question types (comment and pagebreak)
        $my_temp_questions_data = $temp_questions_data == null ? array() : $temp_questions_data;
        $questions_data = array();

        foreach ($my_temp_questions_data as $key => & $value) {
            if ($value['type'] != 'comment' && $value['type'] != 'pagebreak') {
                $questions_data[$value['sort']] = $value;
            }
        }

        // Counting the number of questions that are relevant for the reporting
        $survey_data['number_of_questions'] = count($questions_data);

        if ($action == 'questionreport') {
            self::display_question_report($survey_data);
        }
        if ($action == 'userreport') {
            self::display_user_report($people_filled, $survey_data);
        }
        if ($action == 'comparativereport') {
            self::display_comparative_report();
        }
        if ($action == 'completereport') {
            self::display_complete_report($survey_data);
        }
        if ($action == 'deleteuserreport') {
            self::delete_user_report($_GET['survey_id'], $_GET['user']);
        }
    }

    /**
     * This function deletes the report of an user who wants to retake the survey
     * @param integer $survey_id
     * @param integer $user_id
     * @return void
     * @author Christian Fasanando Flores <christian.fasanando@dokeos.com>
     * @version November 2008
     */
    public static function delete_user_report($survey_id, $user_id)
    {
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);
        $table_survey_invitation = Database::get_course_table(TABLE_SURVEY_INVITATION);
        $table_survey = Database::get_course_table(TABLE_SURVEY);

        $course_id = api_get_course_int_id();
        $survey_id = (int) $survey_id;
        $user_id = Database::escape_string($user_id);

        if (!empty($survey_id) && !empty($user_id)) {
            // delete data from survey_answer by user_id and survey_id
            $sql = "DELETE FROM $table_survey_answer
			        WHERE c_id = $course_id AND survey_id = '".$survey_id."' AND user = '".$user_id."'";
            Database::query($sql);
            // update field answered from survey_invitation by user_id and survey_id
            $sql = "UPDATE $table_survey_invitation SET answered = '0'
			        WHERE
			            c_id = $course_id AND
			            survey_code = (
                            SELECT code FROM $table_survey
                            WHERE
                                c_id = $course_id AND
                                survey_id = '".$survey_id."'
                        ) AND
			            user = '".$user_id."'";
            $result = Database::query($sql);
        }

        if ($result !== false) {

The variable $result does not seem to be defined for all execution paths leading up to this point.

            $message = get_lang('SurveyUserAnswersHaveBeenRemovedSuccessfully').'<br />
					<a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action=userreport&survey_id='
                .$survey_id.'">'.
                get_lang('GoBack').'</a>';
            echo Display::return_message($message, 'confirmation', false);
        }
    }

    /**
     * This function displays the user report which is basically nothing more
     * than a one-page display of all the questions
     * of the survey that is filled with the answers of the person who filled the survey.
     *
     * @return string html code of the one-page survey with the answers of the selected user
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007 - Updated March 2008
     */
    public static function display_user_report($people_filled, $survey_data)
    {
        // Database table definitions
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $table_survey_question_option = Database::get_course_table(TABLE_SURVEY_QUESTION_OPTION);
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);
        $surveyId = isset($_GET['survey_id']) ? (int) $_GET['survey_id'] : 0;

        // Actions bar
        echo '<div class="actions">';
        echo '<a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?survey_id='.$surveyId.'&'.api_get_cidreq().'">'.
            Display::return_icon('back.png', get_lang('BackTo').' '.get_lang('ReportingOverview'), '', ICON_SIZE_MEDIUM)
            .'</a>';
        if (isset($_GET['user'])) {
            if (api_is_allowed_to_edit()) {
                // The delete link
                echo '<a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action=deleteuserreport&survey_id='
                    .$surveyId.'&'.api_get_cidreq().'&user='.Security::remove_XSS($_GET['user']).'" >'.
                    Display::return_icon('delete.png', get_lang('Delete'), '', ICON_SIZE_MEDIUM).'</a>';
            }

            // Export the user report
            echo '<a href="javascript: void(0);" onclick="document.form1a.submit();">'
                .Display::return_icon('export_csv.png', get_lang('ExportAsCSV'), '', ICON_SIZE_MEDIUM).'</a> ';
            echo '<a href="javascript: void(0);" onclick="document.form1b.submit();">'
                .Display::return_icon('export_excel.png', get_lang('ExportAsXLS'), '', ICON_SIZE_MEDIUM).'</a> ';
            echo '<form id="form1a" name="form1a" method="post" action="'.api_get_self().'?action='
                .Security::remove_XSS($_GET['action']).'&survey_id='.$surveyId.'&'.api_get_cidreq().'&user_id='
                .Security::remove_XSS($_GET['user']).'">';
            echo '<input type="hidden" name="export_report" value="export_report">';
            echo '<input type="hidden" name="export_format" value="csv">';
            echo '</form>';
            echo '<form id="form1b" name="form1b" method="post" action="'.api_get_self().'?action='
                .Security::remove_XSS($_GET['action']).'&survey_id='.$surveyId.'&'.api_get_cidreq().'&user_id='
                .Security::remove_XSS($_GET['user']).'">';
            echo '<input type="hidden" name="export_report" value="export_report">';
            echo '<input type="hidden" name="export_format" value="xls">';
            echo '</form>';
            echo '<form id="form2" name="form2" method="post" action="'.api_get_self().'?action='
                .Security::remove_XSS($_GET['action']).'&survey_id='.$surveyId.'&'.api_get_cidreq().'">';
        }
        echo '</div>';

        // Step 1: selection of the user
        echo "<script>
        function jumpMenu(targ,selObj,restore) {
            eval(targ+\".location='\"+selObj.options[selObj.selectedIndex].value+\"'\");
            if (restore) selObj.selectedIndex=0;
        }
		</script>";
        echo get_lang('SelectUserWhoFilledSurvey').'<br />';

        echo '<select name="user" onchange="jumpMenu(\'parent\',this,0)">';
        echo '<option value="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action='
            .Security::remove_XSS($_GET['action']).'&survey_id='.intval($_GET['survey_id']).'">'
            .get_lang('SelectUser').'</option>';

        foreach ($people_filled as $key => & $person) {
            if ($survey_data['anonymous'] == 0) {
                $name = $person['user_info']['complete_name_with_username'];
                $id = $person['user_id'];
                if ($id == '') {
                    $id = $person['invited_user'];
                    $name = $person['invited_user'];
                }
            } else {
                $name = get_lang('Anonymous').' '.($key + 1);
                $id = $person;
            }
            echo '<option value="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action='
                .Security::remove_XSS($_GET['action']).'&survey_id='.intval($_GET['survey_id']).'&user='
                .Security::remove_XSS($id).'" ';
            if (isset($_GET['user']) && $_GET['user'] == $id) {
                echo 'selected="selected"';
            }
            echo '>'.$name.'</option>';
        }
        echo '</select>';

        $course_id = api_get_course_int_id();
        // Step 2: displaying the survey and the answer of the selected users
        if (isset($_GET['user'])) {
            echo Display::return_message(
                get_lang('AllQuestionsOnOnePage'),
                'normal',
                false
            );

            // Getting all the questions and options
            $sql = "SELECT
			            survey_question.question_id,
			            survey_question.survey_id,
			            survey_question.survey_question,
			            survey_question.display,
			            survey_question.max_value,
			            survey_question.sort,
			            survey_question.type,
                        survey_question_option.question_option_id,
                        survey_question_option.option_text,
                        survey_question_option.sort as option_sort
					FROM $table_survey_question survey_question
					LEFT JOIN $table_survey_question_option survey_question_option
					ON
					    survey_question.question_id = survey_question_option.question_id AND
					    survey_question_option.c_id = $course_id
					WHERE
					    survey_question.survey_id = '".intval($_GET['survey_id'])."' AND
                        survey_question.c_id = $course_id
					ORDER BY survey_question.sort, survey_question_option.sort ASC";
            $result = Database::query($sql);
            while ($row = Database::fetch_array($result, 'ASSOC')) {
                if ($row['type'] != 'pagebreak') {
                    $questions[$row['sort']]['question_id'] = $row['question_id'];
                    $questions[$row['sort']]['survey_id'] = $row['survey_id'];
                    $questions[$row['sort']]['survey_question'] = $row['survey_question'];
                    $questions[$row['sort']]['display'] = $row['display'];
                    $questions[$row['sort']]['type'] = $row['type'];
                    $questions[$row['sort']]['maximum_score'] = $row['max_value'];
                    $questions[$row['sort']]['options'][$row['question_option_id']] = $row['option_text'];
                }
            }

            // Getting all the answers of the user
            $sql = "SELECT * FROM $table_survey_answer
			        WHERE
                        c_id = $course_id AND
                        survey_id = '".intval($_GET['survey_id'])."' AND
                        user = '".Database::escape_string($_GET['user'])."'";
            $result = Database::query($sql);
            while ($row = Database::fetch_array($result, 'ASSOC')) {
                $answers[$row['question_id']][] = $row['option_id'];
                $all_answers[$row['question_id']][] = $row;
            }

            // Displaying all the questions

            foreach ($questions as & $question) {

The variable $questions does not seem to be defined for all execution paths leading up to this point.

                // If the question type is a scoring then we have to format the answers differently
                switch ($question['type']) {
                    case 'score':
                        $finalAnswer = array();
                        if (is_array($question) && is_array($all_answers)) {

The variable $all_answers does not seem to be defined for all execution paths leading up to this point.

                            foreach ($all_answers[$question['question_id']] as $key => & $answer_array) {
                                $finalAnswer[$answer_array['option_id']] = $answer_array['value'];
                            }
                        }
                        break;
                    case 'multipleresponse':
                        $finalAnswer = isset($answers[$question['question_id']])
                            ? $answers[$question['question_id']]

The variable $answers does not seem to be defined for all execution paths leading up to this point.

                            : '';
                        break;
                    default:
                        $finalAnswer = '';
                        if (isset($all_answers[$question['question_id']])) {
                            $finalAnswer = $all_answers[$question['question_id']][0]['option_id'];
                        }
                        break;
                }

                $ch_type = 'ch_'.$question['type'];
                /** @var survey_question $display */
                $display = new $ch_type;

                $url = api_get_self();
                $form = new FormValidator('question', 'post', $url);
                $form->addHtml('<div class="survey_question_wrapper"><div class="survey_question">');
                $form->addHtml($question['survey_question']);
                $display->render($form, $question, $finalAnswer);

It seems like $finalAnswer can also be of type string; however, parameter $answers of survey_question::render() does only seem to accept array, maybe add an additional type check?

                $form->addHtml('</div></div>');
                $form->display();
            }
        }
    }

    /**
     * This function displays the report by question.
     *
     * It displays a table with all the options of the question and the number of users who have answered positively on
     * the option. The number of users who answered positive on a given option is expressed in an absolute number, in a
     * percentage of the total and graphically using bars By clicking on the absolute number you get a list with the
     * persons who have answered this. You can then click on the name of the person and you will then go to the report
     * by user where you see all the answers of that user.
     *
     * @param    array    All the survey data
     * @return   string    html code that displays the report by question
     * @todo allow switching between horizontal and vertical.
     * @todo multiple response: percentage are probably not OK
     * @todo the question and option text have to be shortened and should expand when the user clicks on it.
     * @todo the pagebreak and comment question types should not be shown => removed from $survey_data before
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007 - Updated March 2008
     */
    public static function display_question_report($survey_data)
    {
        $singlePage = isset($_GET['single_page']) ? intval($_GET['single_page']) : 0;
        $course_id = api_get_course_int_id();
        // Database table definitions
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $table_survey_question_option = Database::get_course_table(TABLE_SURVEY_QUESTION_OPTION);
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);

        // Determining the offset of the sql statement (the n-th question of the survey)
        $offset = !isset($_GET['question']) ? 0 : intval($_GET['question']);
        $currentQuestion = isset($_GET['question']) ? intval($_GET['question']) : 0;
        $questions = array();
        $surveyId = intval($_GET['survey_id']);
        $action = Security::remove_XSS($_GET['action']);

        echo '<div class="actions">';
        echo '<a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?survey_id='.$surveyId.'&'.api_get_cidreq().'">'.
            Display::return_icon(
                'back.png',
                get_lang('BackTo').' '.get_lang('ReportingOverview'),
                '',
                ICON_SIZE_MEDIUM
            ).'</a>';
        echo '</div>';

        if ($survey_data['number_of_questions'] > 0) {
            $limitStatement = null;
            if (!$singlePage) {
                echo '<div id="question_report_questionnumbers" class="pagination">';
                if ($currentQuestion != 0) {
                    echo '<li><a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action='.$action.'&'
                        .api_get_cidreq().'&survey_id='.$surveyId.'&question='.($offset - 1).'">'
                        .get_lang('PreviousQuestion').'</a></li>';
                }

                for ($i = 1; $i <= $survey_data['number_of_questions']; $i++) {
                    if ($offset != $i - 1) {
                        echo '<li><a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action='.$action.'&'
                            .api_get_cidreq().'&survey_id='.$surveyId.'&question='.($i - 1).'">'.$i.'</a></li>';
                    } else {
                        echo '<li class="disabled"s><a href="#">'.$i.'</a></li>';
                    }
                }
                if ($currentQuestion < ($survey_data['number_of_questions'] - 1)) {
                    echo '<li><a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action='.$action.'&'
                        .api_get_cidreq().'&survey_id='.$surveyId.'&question='.($offset + 1).'">'
                        .get_lang('NextQuestion').'</li></a>';
                }
                echo '</ul>';
                echo '</div>';
                $limitStatement = " LIMIT $offset, 1";
            }

            // Getting the question information
            $sql = "SELECT * FROM $table_survey_question
			        WHERE
			            c_id = $course_id AND
                        survey_id='".intval($_GET['survey_id'])."' AND
                        type <>'pagebreak' AND 
                        type <>'comment'
                    ORDER BY sort ASC
                    $limitStatement";
            $result = Database::query($sql);
            while ($row = Database::fetch_array($result)) {
                $questions[$row['question_id']] = $row;
            }
        }

        foreach ($questions as $question) {
            $chartData = array();
            $options = array();
            echo '<div class="title-question">';
            echo strip_tags(isset($question['survey_question']) ? $question['survey_question'] : null);
            echo '</div>';

            if ($question['type'] == 'score') {
                /** @todo This function should return the options as this is needed further in the code */
                $options = self::display_question_report_score($survey_data, $question, $offset);

Are you sure the assignment to $options is correct as self::display_question_report_score($survey_data, $question, $offset) targeting SurveyUtil::display_question_report_score() seems to always return null.

            } elseif ($question['type'] == 'open') {
                /** @todo Also get the user who has answered this */
                $sql = "SELECT * FROM $table_survey_answer
                        WHERE
                            c_id = $course_id AND
                            survey_id='".intval($_GET['survey_id'])."' AND
                            question_id = '".intval($question['question_id'])."'";
                $result = Database::query($sql);
                while ($row = Database::fetch_array($result, 'ASSOC')) {
                    echo $row['option_id'].'<hr noshade="noshade" size="1" />';
                }
            } else {
                // Getting the options ORDER BY sort ASC
                $sql = "SELECT * FROM $table_survey_question_option
                        WHERE
                            c_id = $course_id AND
                            survey_id='".intval($_GET['survey_id'])."'
                            AND question_id = '".intval($question['question_id'])."'
                        ORDER BY sort ASC";
                $result = Database::query($sql);
                while ($row = Database::fetch_array($result, 'ASSOC')) {
                    $options[$row['question_option_id']] = $row;
                }
                // Getting the answers
                $sql = "SELECT *, count(answer_id) as total FROM $table_survey_answer
                        WHERE
                            c_id = $course_id AND
                            survey_id='".intval($_GET['survey_id'])."'
                            AND question_id = '".intval($question['question_id'])."'
                        GROUP BY option_id, value";
                $result = Database::query($sql);
                $number_of_answers = array();
                $data = array();
                while ($row = Database::fetch_array($result, 'ASSOC')) {
                    if (!isset($number_of_answers[$row['question_id']])) {
                        $number_of_answers[$row['question_id']] = 0;
                    }
                    $number_of_answers[$row['question_id']] += $row['total'];
                    $data[$row['option_id']] = $row;
                }

                foreach ($options as $option) {
                    $optionText = strip_tags($option['option_text']);
                    $optionText = html_entity_decode($optionText);
                    $votes = isset($data[$option['question_option_id']]['total']) ?
                        $data[$option['question_option_id']]['total'] : '0';
                    array_push($chartData, array('option' => $optionText, 'votes' => $votes));
                }
                $chartContainerId = 'chartContainer'.$question['question_id'];
                echo '<div id="'.$chartContainerId.'" class="col-md-12">';
                echo self::drawChart($chartData, false, $chartContainerId);

                // displaying the table: headers
                echo '<table class="display-survey table">';
                echo '	<tr>';
                echo '		<th>&nbsp;</th>';
                echo '		<th>'.get_lang('AbsoluteTotal').'</th>';
                echo '		<th>'.get_lang('Percentage').'</th>';
                echo '		<th>'.get_lang('VisualRepresentation').'</th>';
                echo '	<tr>';

                // Displaying the table: the content
                if (is_array($options)) {
                    foreach ($options as $key => & $value) {
                        $absolute_number = null;
                        if (isset($data[$value['question_option_id']])) {
                            $absolute_number = $data[$value['question_option_id']]['total'];
                        }
                        if ($question['type'] == 'percentage' && empty($absolute_number)) {
                            continue;
                        }
                        $number_of_answers[$option['question_id']] = isset($number_of_answers[$option['question_id']])

The variable $option does not seem to be defined for all execution paths leading up to this point.

                            ? $number_of_answers[$option['question_id']]
                            : 0;
                        if ($number_of_answers[$option['question_id']] == 0) {
                            $answers_number = 0;
                        } else {
                            $answers_number = $absolute_number / $number_of_answers[$option['question_id']] * 100;
                        }
                        echo '	<tr>';
                        echo '		<td class="center">'.$value['option_text'].'</td>';
                        echo '		<td class="center">';
                        if ($absolute_number != 0) {

It seems like you are loosely comparing $absolute_number of type null|mixed to 0; this is ambiguous as not only 0 == 0 is true, but null == 0 is true, too. Consider using a strict comparison ===.

                            echo '<a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action='.$action
                                .'&survey_id='.$surveyId.'&question='.$offset.'&viewoption='
                                .$value['question_option_id'].'">'.$absolute_number.'</a>';
                        } else {
                            echo '0';
                        }

                        echo '      </td>';
                        echo '		<td class="center">'.round($answers_number, 2).' %</td>';
                        echo '		<td class="center">';
                        $size = $answers_number * 2;
                        if ($size > 0) {
                            echo '<div style="border:1px solid #264269; background-color:#aecaf4; height:10px; width:'
                                .$size.'px">&nbsp;</div>';
                        } else {
                            echo '<div style="text-align: left;">'.get_lang("NoDataAvailable").'</div>';
                        }
                        echo ' </td>';
                        echo ' </tr>';
                    }
                }
                // displaying the table: footer (totals)
                echo '	<tr>';
                echo '		<td class="total"><b>'.get_lang('Total').'</b></td>';
                echo '		<td class="total"><b>'
                    .($number_of_answers[$option['question_id']] == 0
                        ? '0'
                        : $number_of_answers[$option['question_id']])
                    .'</b></td>';
                echo '		<td class="total">&nbsp;</td>';
                echo '		<td class="total">&nbsp;</td>';
                echo '	</tr>';
                echo '</table>';
                echo '</div>';
            }
        }
        if (isset($_GET['viewoption'])) {
            echo '<div class="answered-people">';
            echo '<h4>'.get_lang('PeopleWhoAnswered').': '
                .strip_tags($options[Security::remove_XSS($_GET['viewoption'])]['option_text']).'</h4>';

The variable $options seems to be defined by a foreach iteration on line 572. Are you sure the iterator is never empty, otherwise this variable is not defined?

            if (is_numeric($_GET['value'])) {
                $sql_restriction = "AND value='".Database::escape_string($_GET['value'])."'";
            }

            $sql = "SELECT user FROM $table_survey_answer
                    WHERE
                        c_id = $course_id AND
                        option_id = '".Database::escape_string($_GET['viewoption'])."'
                        $sql_restriction";

The variable $sql_restriction does not seem to be defined for all execution paths leading up to this point.

            $result = Database::query($sql);
            echo '<ul>';
            while ($row = Database::fetch_array($result, 'ASSOC')) {
                $user_info = api_get_user_info($row['user']);
                echo '<li><a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action=userreport&survey_id='
                    .$surveyId.'&user='.$row['user'].'">'
                    .$user_info['complete_name_with_username']
                    .'</a></li>';
            }
            echo '</ul>';
            echo '</div>';
        }
    }

    /**
     * Display score data about a survey question
     * @param    array    Question info
     * @param    integer    The offset of results shown
     * @return   void    (direct output)
     */
    public static function display_question_report_score($survey_data, $question, $offset)
    {
        // Database table definitions
        $action = isset($_GET['action']) ? Security::remove_XSS($_GET['action']) : '';
        $table_survey_question_option = Database::get_course_table(TABLE_SURVEY_QUESTION_OPTION);
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);
        $course_id = api_get_course_int_id();

        // Getting the options
        $sql = "SELECT * FROM $table_survey_question_option
                WHERE
                    c_id = $course_id AND
                    survey_id='".intval($_GET['survey_id'])."' AND
                    question_id = '".intval($question['question_id'])."'
                ORDER BY sort ASC";
        $result = Database::query($sql);
        while ($row = Database::fetch_array($result)) {
            $options[$row['question_option_id']] = $row;
        }

        // Getting the answers
        $sql = "SELECT *, count(answer_id) as total 
                FROM $table_survey_answer
                WHERE
                   c_id = $course_id AND
                   survey_id='".intval($_GET['survey_id'])."' AND
                   question_id = '".Database::escape_string($question['question_id'])."'
                GROUP BY option_id, value";
        $result = Database::query($sql);
        $number_of_answers = 0;
        while ($row = Database::fetch_array($result)) {
            $number_of_answers += $row['total'];
            $data[$row['option_id']][$row['value']] = $row;
        }

        $chartData = array();
        foreach ($options as $option) {

The variable $options does not seem to be defined for all execution paths leading up to this point.

            $optionText = strip_tags($option['option_text']);
            $optionText = html_entity_decode($optionText);
            for ($i = 1; $i <= $question['max_value']; $i++) {
                $votes = $data[$option['question_option_id']][$i]['total'];

The variable $data does not seem to be defined for all execution paths leading up to this point.

                if (empty($votes)) {
                    $votes = '0';
                }
                array_push(
                    $chartData,
                    array(
                        'serie' => $optionText,
                        'option' => $i,
                        'votes' => $votes
                    )
                );
            }
        }
        echo '<div id="chartContainer" class="col-md-12">';
        echo self::drawChart($chartData, true);
        echo '</div>';

        // Displaying the table: headers
        echo '<table class="data_table">';
        echo '	<tr>';
        echo '		<th>&nbsp;</th>';
        echo '		<th>'.get_lang('Score').'</th>';
        echo '		<th>'.get_lang('AbsoluteTotal').'</th>';
        echo '		<th>'.get_lang('Percentage').'</th>';
        echo '		<th>'.get_lang('VisualRepresentation').'</th>';
        echo '	<tr>';
        // Displaying the table: the content
        foreach ($options as $key => & $value) {
            for ($i = 1; $i <= $question['max_value']; $i++) {
                $absolute_number = $data[$value['question_option_id']][$i]['total'];
                echo '	<tr>';
                echo '		<td>'.$value['option_text'].'</td>';
                echo '		<td>'.$i.'</td>';
                echo '		<td><a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?action='.$action
                    .'&survey_id='.intval($_GET['survey_id']).'&question='.Security::remove_XSS($offset)
                    .'&viewoption='.$value['question_option_id'].'&value='.$i.'">'.$absolute_number.'</a></td>';
                echo '		<td>'.round($absolute_number / $number_of_answers * 100, 2).' %</td>';
                echo '		<td>';
                $size = ($absolute_number / $number_of_answers * 100 * 2);
                if ($size > 0) {
                    echo '<div style="border:1px solid #264269; background-color:#aecaf4; height:10px; width:'.$size.'px">&nbsp;</div>';
                }
                echo '		</td>';
                echo '	</tr>';
            }
        }
        // Displaying the table: footer (totals)
        echo '	<tr>';
        echo '		<td style="border-top:1px solid black"><b>'.get_lang('Total').'</b></td>';
        echo '		<td style="border-top:1px solid black">&nbsp;</td>';
        echo '		<td style="border-top:1px solid black"><b>'.$number_of_answers.'</b></td>';
        echo '		<td style="border-top:1px solid black">&nbsp;</td>';
        echo '		<td style="border-top:1px solid black">&nbsp;</td>';
        echo '	</tr>';

        echo '</table>';
    }

    /**
     * This functions displays the complete reporting
     * @return string    HTML code
     * @todo open questions are not in the complete report yet.
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007
     */
    public static function display_complete_report($survey_data)
    {
        // Database table definitions
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $table_survey_question_option = Database::get_course_table(TABLE_SURVEY_QUESTION_OPTION);
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);

        $surveyId = isset($_GET['survey_id']) ? intval($_GET['survey_id']) : 0;
        $action = isset($_GET['action']) ? Security::remove_XSS($_GET['action']) : '';

        // Actions bar
        echo '<div class="actions">';
        echo '<a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?survey_id='.$surveyId.'&'.api_get_cidreq().'">'
            .Display::return_icon(
                'back.png',
                get_lang('BackTo').' '.get_lang('ReportingOverview'),
                [],
                ICON_SIZE_MEDIUM
            )
            .'</a>';
        echo '<a class="survey_export_link" href="javascript: void(0);" onclick="document.form1a.submit();">'
            .Display::return_icon('export_csv.png', get_lang('ExportAsCSV'), '', ICON_SIZE_MEDIUM).'</a>';
        echo '<a class="survey_export_link" href="javascript: void(0);" onclick="document.form1b.submit();">'
            .Display::return_icon('export_excel.png', get_lang('ExportAsXLS'), '', ICON_SIZE_MEDIUM).'</a>';
        echo '</div>';

        // The form
        echo '<form id="form1a" name="form1a" method="post" action="'.api_get_self().'?action='.$action.'&survey_id='
            .$surveyId.'&'.api_get_cidreq().'">';
        echo '<input type="hidden" name="export_report" value="export_report">';
        echo '<input type="hidden" name="export_format" value="csv">';
        echo '</form>';
        echo '<form id="form1b" name="form1b" method="post" action="'.api_get_self().'?action='.$action.'&survey_id='
            .$surveyId.'&'.api_get_cidreq().'">';
        echo '<input type="hidden" name="export_report" value="export_report">';
        echo '<input type="hidden" name="export_format" value="xls">';
        echo '</form>';

        echo '<form id="form2" name="form2" method="post" action="'.api_get_self().'?action='.$action.'&survey_id='
            .$surveyId.'&'.api_get_cidreq().'">';

        // The table
        echo '<br /><table class="data_table" border="1">';
        // Getting the number of options per question
        echo '	<tr>';
        echo '		<th>';
        if ((isset($_POST['submit_question_filter']) && $_POST['submit_question_filter']) ||
            (isset($_POST['export_report']) && $_POST['export_report'])
        ) {
            echo '<button class="cancel" type="submit" name="reset_question_filter" value="'
                .get_lang('ResetQuestionFilter').'">'.get_lang('ResetQuestionFilter').'</button>';
        }
        echo '<button class="save" type="submit" name="submit_question_filter" value="'.get_lang('SubmitQuestionFilter')
            .'">'.get_lang('SubmitQuestionFilter').'</button>';
        echo '</th>';

        $display_extra_user_fields = false;
        if (!(isset($_POST['submit_question_filter']) && $_POST['submit_question_filter'] ||
                isset($_POST['export_report']) && $_POST['export_report']) ||
            !empty($_POST['fields_filter'])
        ) {
            // Show user fields section with a big th colspan that spans over all fields
            $extra_user_fields = UserManager::get_extra_fields(
                0,
                0,
                5,
                'ASC',
                false,
                true
            );
            $num = count($extra_user_fields);
            if ($num > 0) {
                echo '<th '.($num > 0 ? ' colspan="'.$num.'"' : '').'>';
                echo '<label><input type="checkbox" name="fields_filter" value="1" checked="checked"/> ';
                echo get_lang('UserFields');
                echo '</label>';
                echo '</th>';
                $display_extra_user_fields = true;
            }
        }

        $course_id = api_get_course_int_id();
        $sql = "SELECT q.question_id, q.type, q.survey_question, count(o.question_option_id) as number_of_options
				FROM $table_survey_question q 
				LEFT JOIN $table_survey_question_option o
				ON q.question_id = o.question_id
				WHERE 
				    q.survey_id = '".$surveyId."' AND
				    q.c_id = $course_id AND
				    o.c_id = $course_id
				GROUP BY q.question_id
				ORDER BY q.sort ASC";
        $result = Database::query($sql);
        $questions = [];
        while ($row = Database::fetch_array($result)) {
            // We show the questions if
            // 1. there is no question filter and the export button has not been clicked
            // 2. there is a quesiton filter but the question is selected for display
            if (!(isset($_POST['submit_question_filter']) && $_POST['submit_question_filter']) ||
                (is_array($_POST['questions_filter']) && in_array($row['question_id'], $_POST['questions_filter']))
            ) {
                // We do not show comment and pagebreak question types
                if ($row['type'] != 'comment' && $row['type'] != 'pagebreak') {
                    echo ' <th';
                    // <hub> modified tst to include percentage
                    if ($row['number_of_options'] > 0 && $row['type'] != 'percentage') {
                        // </hub>
                        echo ' colspan="'.$row['number_of_options'].'"';
                    }
                    echo '>';

                    echo '<label><input type="checkbox" name="questions_filter[]" value="'.$row['question_id']
                        .'" checked="checked"/> ';
                    echo $row['survey_question'];
                    echo '</label>';
                    echo '</th>';
                }
                // No column at all if it's not a question
            }
            $questions[$row['question_id']] = $row;
        }
        echo '	</tr>';
        // Getting all the questions and options
        echo '	<tr>';
        echo '		<th>&nbsp;</th>'; // the user column

        if (!(isset($_POST['submit_question_filter']) && $_POST['submit_question_filter'] ||
                isset($_POST['export_report']) && $_POST['export_report']) || !empty($_POST['fields_filter'])) {
            //show the fields names for user fields
            foreach ($extra_user_fields as & $field) {

The variable $extra_user_fields does not seem to be defined for all execution paths leading up to this point.

                echo '<th>'.$field[3].'</th>';
            }
        }

        // cells with option (none for open question)
        $sql = "SELECT 	
                    sq.question_id, sq.survey_id,
                    sq.survey_question, sq.display,
                    sq.sort, sq.type, sqo.question_option_id,
                    sqo.option_text, sqo.sort as option_sort
				FROM $table_survey_question sq
				LEFT JOIN $table_survey_question_option sqo
				ON sq.question_id = sqo.question_id
				WHERE
				    sq.survey_id = '".$surveyId."' AND
                    sq.c_id = $course_id AND
                    sqo.c_id = $course_id
				ORDER BY sq.sort ASC, sqo.sort ASC";
        $result = Database::query($sql);

        $display_percentage_header = 1;
        $possible_answers = [];
        // in order to display only once the cell option (and not 100 times)
        while ($row = Database::fetch_array($result)) {
            // We show the options if
            // 1. there is no question filter and the export button has not been clicked
            // 2. there is a question filter but the question is selected for display
            if (!(isset($_POST['submit_question_filter']) && $_POST['submit_question_filter']) ||
                (is_array($_POST['questions_filter']) && in_array($row['question_id'], $_POST['questions_filter']))
            ) {
                // <hub> modif 05-05-2010
                // we do not show comment and pagebreak question types
                if ($row['type'] == 'open') {
                    echo '<th>&nbsp;-&nbsp;</th>';
                    $possible_answers[$row['question_id']][$row['question_option_id']] = $row['question_option_id'];
                    $display_percentage_header = 1;
                } elseif ($row['type'] == 'percentage' && $display_percentage_header) {
                    echo '<th>&nbsp;%&nbsp;</th>';
                    $possible_answers[$row['question_id']][$row['question_option_id']] = $row['question_option_id'];
                    $display_percentage_header = 0;
                } elseif ($row['type'] == 'percentage') {
                    $possible_answers[$row['question_id']][$row['question_option_id']] = $row['question_option_id'];
                } elseif ($row['type'] <> 'comment' && $row['type'] <> 'pagebreak' && $row['type'] <> 'percentage') {
                    echo '<th>';
                    echo $row['option_text'];
                    echo '</th>';
                    $possible_answers[$row['question_id']][$row['question_option_id']] = $row['question_option_id'];
                    $display_percentage_header = 1;
                }
                //no column at all if the question was not a question
                // </hub>
            }
        }

        echo '	</tr>';

        // Getting all the answers of the users
        $old_user = '';
        $answers_of_user = array();
        $sql = "SELECT * FROM $table_survey_answer
                WHERE
                    c_id = $course_id AND
                    survey_id='".$surveyId."'
                ORDER BY answer_id, user ASC";
        $result = Database::query($sql);
        $i = 1;
        while ($row = Database::fetch_array($result)) {
            if ($old_user != $row['user'] && $old_user != '') {
                $userParam = $old_user;
                if ($survey_data['anonymous'] != 0) {
                    $userParam = $i;
                    $i++;
                }
                self::display_complete_report_row(
                    $survey_data,
                    $possible_answers,
                    $answers_of_user,
                    $userParam,
                    $questions,
                    $display_extra_user_fields
                );
                $answers_of_user = array();
            }
            if (isset($questions[$row['question_id']]) && $questions[$row['question_id']]['type'] != 'open') {
                $answers_of_user[$row['question_id']][$row['option_id']] = $row;
            } else {
                $answers_of_user[$row['question_id']][0] = $row;
            }
            $old_user = $row['user'];
        }
        $userParam = $old_user;
        if ($survey_data['anonymous'] != 0) {
            $userParam = $i;
            $i++;
        }
        self::display_complete_report_row(
            $survey_data,
            $possible_answers,
            $answers_of_user,
            $userParam,
            $questions,
            $display_extra_user_fields
        );
        // This is to display the last user
        echo '</table>';
        echo '</form>';
    }

    /**
     * This function displays a row (= a user and his/her answers) in the table of the complete report.
     *
     * @param array $survey_data
     * @param array    Possible options
     * @param array    User answers
     * @param mixed    User ID or user details string
     * @param boolean  Whether to show extra user fields or not
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007 - Updated March 2008
     */
    public static function display_complete_report_row(
        $survey_data,
        $possible_options,
        $answers_of_user,
        $user,
        $questions,
        $display_extra_user_fields = false
    ) {
        $user = Security::remove_XSS($user);
        echo '<tr>';
        if ($survey_data['anonymous'] == 0) {
            if (intval($user) !== 0) {
                $userInfo = api_get_user_info($user);
                if (!empty($userInfo)) {
                    $user_displayed = $userInfo['complete_name_with_username'];
                } else {
                    $user_displayed = '-';
                }
                echo '<th>
                    <a href="'.api_get_self().'?action=userreport&survey_id='.intval($_GET['survey_id']).'&user='.$user.'">'
                    .$user_displayed.'</a>
                    </th>'; // the user column
            } else {
                echo '<th>'.$user.'</th>'; // the user column
            }
        } else {
            echo '<th>'.get_lang('Anonymous').' '.$user.'</th>';
        }

        if ($display_extra_user_fields) {
            // Show user fields data, if any, for this user
            $user_fields_values = UserManager::get_extra_user_data(
                intval($user),
                false,
                false,
                false,
                true
            );
            foreach ($user_fields_values as & $value) {
                echo '<td align="center">'.$value.'</td>';
            }
        }
        if (is_array($possible_options)) {
            // <hub> modified to display open answers and percentage
            foreach ($possible_options as $question_id => & $possible_option) {
                if ($questions[$question_id]['type'] == 'open') {
                    echo '<td align="center">';
                    echo $answers_of_user[$question_id]['0']['option_id'];
                    echo '</td>';
                } else {
                    foreach ($possible_option as $option_id => & $value) {
                        if ($questions[$question_id]['type'] == 'percentage') {
                            if (!empty($answers_of_user[$question_id][$option_id])) {
                                echo "<td align='center'>";
                                echo $answers_of_user[$question_id][$option_id]['value'];
                                echo "</td>";
                            }
                        } else {
                            echo '<td align="center">';
                            if (!empty($answers_of_user[$question_id][$option_id])) {
                                if ($answers_of_user[$question_id][$option_id]['value'] != 0) {
                                    echo $answers_of_user[$question_id][$option_id]['value'];
                                } else {
                                    echo 'v';
                                }
                            }
                        }
                    }
                }
            }
        }
        echo '</tr>';
    }

    /**
     * Quite similar to display_complete_report(), returns an HTML string
     * that can be used in a csv file
     * @todo consider merging this function with display_complete_report
     * @return    string    The contents of a csv file
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007
     */
    public static function export_complete_report($survey_data, $user_id = 0)
    {
        // Database table definitions
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $table_survey_question_option = Database::get_course_table(TABLE_SURVEY_QUESTION_OPTION);
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);

        // The first column
        $return = ';';

        // Show extra fields blank space (enough for extra fields on next line)
        $extra_user_fields = UserManager::get_extra_fields(
            0,
            0,
            5,
            'ASC',
            false,
            true
        );

        $num = count($extra_user_fields);
        $return .= str_repeat(';', $num);

        $course_id = api_get_course_int_id();

        $sql = "SELECT
                    questions.question_id,
                    questions.type,
                    questions.survey_question,
                    count(options.question_option_id) as number_of_options
				FROM $table_survey_question questions
                LEFT JOIN $table_survey_question_option options
				ON questions.question_id = options.question_id AND options.c_id = $course_id
				WHERE
				    questions.survey_id = '".intval($_GET['survey_id'])."' AND
                    questions.c_id = $course_id
				GROUP BY questions.question_id
				ORDER BY questions.sort ASC";
        $result = Database::query($sql);
        while ($row = Database::fetch_array($result)) {
            // We show the questions if
            // 1. there is no question filter and the export button has not been clicked
            // 2. there is a quesiton filter but the question is selected for display
            if (!(isset($_POST['submit_question_filter'])) ||
                (isset($_POST['submit_question_filter']) &&
                    is_array($_POST['questions_filter']) &&
                    in_array($row['question_id'], $_POST['questions_filter']))
            ) {
                // We do not show comment and pagebreak question types
                if ($row['type'] != 'comment' && $row['type'] != 'pagebreak') {
                    if ($row['number_of_options'] == 0 && $row['type'] == 'open') {
                        $return .= str_replace(
                            "\r\n",
                            '  ',
                            api_html_entity_decode(strip_tags($row['survey_question']), ENT_QUOTES)
                        )
                        .';';
                    } else {
                        for ($ii = 0; $ii < $row['number_of_options']; $ii++) {
                            $return .= str_replace(
                                "\r\n",
                                '  ',
                                api_html_entity_decode(strip_tags($row['survey_question']), ENT_QUOTES)
                            )
                            .';';
                        }
                    }
                }
            }
        }
        $return .= "\n";

        // Getting all the questions and options
        $return .= ';';

        // Show the fields names for user fields
        if (!empty($extra_user_fields)) {
            foreach ($extra_user_fields as & $field) {
                $return .= '"'
                    .str_replace(
                        "\r\n",
                        '  ',
                        api_html_entity_decode(strip_tags($field[3]), ENT_QUOTES)
                    )
                    .'";';
            }
        }

        $sql = "SELECT
		            survey_question.question_id,
		            survey_question.survey_id,
		            survey_question.survey_question,
		            survey_question.display,
		            survey_question.sort,
		            survey_question.type,
                    survey_question_option.question_option_id,
                    survey_question_option.option_text,
                    survey_question_option.sort as option_sort
				FROM $table_survey_question survey_question
				LEFT JOIN $table_survey_question_option survey_question_option
				ON
				    survey_question.question_id = survey_question_option.question_id AND
				    survey_question_option.c_id = $course_id
				WHERE
				    survey_question.survey_id = '".intval($_GET['survey_id'])."' AND
				    survey_question.c_id = $course_id
				ORDER BY survey_question.sort ASC, survey_question_option.sort ASC";
        $result = Database::query($sql);
        $possible_answers = array();
        $possible_answers_type = array();
        while ($row = Database::fetch_array($result)) {
            // We show the options if
            // 1. there is no question filter and the export button has not been clicked
            // 2. there is a question filter but the question is selected for display
            if (!(isset($_POST['submit_question_filter'])) || (
                is_array($_POST['questions_filter']) &&
                in_array($row['question_id'], $_POST['questions_filter']))
            ) {
                // We do not show comment and pagebreak question types
                if ($row['type'] != 'comment' && $row['type'] != 'pagebreak') {
                    $row['option_text'] = str_replace(array("\r", "\n"), array('', ''), $row['option_text']);
                    $return .= api_html_entity_decode(strip_tags($row['option_text']), ENT_QUOTES).';';
                    $possible_answers[$row['question_id']][$row['question_option_id']] = $row['question_option_id'];
                    $possible_answers_type[$row['question_id']] = $row['type'];
                }
            }
        }
        $return .= "\n";

        // Getting all the answers of the users
        $old_user = '';
        $answers_of_user = array();
        $sql = "SELECT * FROM $table_survey_answer
		        WHERE c_id = $course_id AND survey_id='".intval($_GET['survey_id'])."'";
        if ($user_id != 0) {
            $sql .= "AND user='".Database::escape_string($user_id)."' ";
        }
        $sql .= "ORDER BY user ASC";

        $open_question_iterator = 1;
        $result = Database::query($sql);
        while ($row = Database::fetch_array($result)) {
            if ($old_user != $row['user'] && $old_user != '') {
                $return .= self::export_complete_report_row(
                    $survey_data,
                    $possible_answers,
                    $answers_of_user,
                    $old_user,
                    true
                );
                $answers_of_user = array();
            }
            if ($possible_answers_type[$row['question_id']] == 'open') {
                $temp_id = 'open'.$open_question_iterator;
                $answers_of_user[$row['question_id']][$temp_id] = $row;
                $open_question_iterator++;
            } else {
                $answers_of_user[$row['question_id']][$row['option_id']] = $row;
            }
            $old_user = $row['user'];
        }
        // This is to display the last user
        $return .= self::export_complete_report_row(
            $survey_data,
            $possible_answers,
            $answers_of_user,
            $old_user,
            true
        );

        return $return;
    }

    /**
     * Add a line to the csv file
     *
     * @param array Possible answers
     * @param array User's answers
     * @param mixed User ID or user details as string - Used as a string in the result string
     * @param boolean Whether to display user fields or not
     * @return string One line of the csv file
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007
     */

The doc comment User's at position 0 could not be parsed: Unknown type name 'User's' at position 0 in User's.

    public static function export_complete_report_row(
        $survey_data,
        $possible_options,
        $answers_of_user,
        $user,
        $display_extra_user_fields = false
    ) {
        $return = '';
        if ($survey_data['anonymous'] == 0) {
            if (intval($user) !== 0) {
                $userInfo = api_get_user_info($user);
                if (!empty($userInfo)) {
                    $user_displayed = $userInfo['complete_name_with_username'];
                } else {
                    $user_displayed = '-';
                }
                $return .= $user_displayed.';';
            } else {
                $return .= $user.';';
            }
        } else {
            $return .= '-;'; // The user column
        }

        if ($display_extra_user_fields) {
            // Show user fields data, if any, for this user
            $user_fields_values = UserManager::get_extra_user_data(
                $user,
                false,
                false,
                false,
                true
            );
            foreach ($user_fields_values as & $value) {
                $return .= '"'.str_replace('"', '""', api_html_entity_decode(strip_tags($value), ENT_QUOTES)).'";';
            }
        }

        if (is_array($possible_options)) {
            foreach ($possible_options as $question_id => $possible_option) {
                if (is_array($possible_option) && count($possible_option) > 0) {
                    foreach ($possible_option as $option_id => & $value) {
                        $my_answer_of_user = !isset($answers_of_user[$question_id]) || isset($answers_of_user[$question_id]) && $answers_of_user[$question_id] == null ? array() : $answers_of_user[$question_id];
                        $key = array_keys($my_answer_of_user);
                        if (isset($key[0]) && substr($key[0], 0, 4) == 'open') {
                            $return .= '"'.
                                str_replace(
                                    '"',
                                    '""',
                                    api_html_entity_decode(
                                        strip_tags(
                                            $answers_of_user[$question_id][$key[0]]['option_id']
                                        ),
                                        ENT_QUOTES
                                    )
                                ).
                                '"';
                        } elseif (!empty($answers_of_user[$question_id][$option_id])) {
                            //$return .= 'v';
                            if ($answers_of_user[$question_id][$option_id]['value'] != 0) {
                                $return .= $answers_of_user[$question_id][$option_id]['value'];
                            } else {
                                $return .= 'v';
                            }
                        }
                        $return .= ';';
                    }
                }
            }
        }
        $return .= "\n";

        return $return;
    }

    /**
     * Quite similar to display_complete_report(), returns an HTML string
     * that can be used in a csv file
     * @todo consider merging this function with display_complete_report
     * @return string The contents of a csv file
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007
     */
    public static function export_complete_report_xls($survey_data, $filename, $user_id = 0)
    {
        $course_id = api_get_course_int_id();
        $surveyId = isset($_GET['survey_id']) ? (int) $_GET['survey_id'] : 0;

        if (empty($course_id) || empty($surveyId)) {
            return false;

The expression return false returns the type false which is incompatible with the documented return type string.

        }

        $spreadsheet = new PHPExcel();
        $spreadsheet->setActiveSheetIndex(0);
        $worksheet = $spreadsheet->getActiveSheet();
        $line = 1;
        $column = 1; // Skip the first column (row titles)

        // Show extra fields blank space (enough for extra fields on next line)
        // Show user fields section with a big th colspan that spans over all fields
        $extra_user_fields = UserManager::get_extra_fields(
            0,
            0,
            5,
            'ASC',
            false,
            true
        );
        $num = count($extra_user_fields);
        for ($i = 0; $i < $num; $i++) {
            $worksheet->setCellValueByColumnAndRow($column, $line, '');
            $column++;
        }

        $display_extra_user_fields = true;

        // Database table definitions
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $table_survey_question_option = Database::get_course_table(TABLE_SURVEY_QUESTION_OPTION);
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);

        // First line (questions)
        $sql = "SELECT
                    questions.question_id,
                    questions.type,
                    questions.survey_question,
                    count(options.question_option_id) as number_of_options
				FROM $table_survey_question questions
				LEFT JOIN $table_survey_question_option options
                ON questions.question_id = options.question_id AND options.c_id = $course_id
				WHERE
				    questions.survey_id = $surveyId AND
				    questions.c_id = $course_id
				GROUP BY questions.question_id
				ORDER BY questions.sort ASC";
        $result = Database::query($sql);
        while ($row = Database::fetch_array($result)) {
            // We show the questions if
            // 1. there is no question filter and the export button has not been clicked
            // 2. there is a quesiton filter but the question is selected for display
            if (!(isset($_POST['submit_question_filter'])) ||
                (isset($_POST['submit_question_filter']) && is_array($_POST['questions_filter']) &&
                in_array($row['question_id'], $_POST['questions_filter']))
            ) {
                // We do not show comment and pagebreak question types
                if ($row['type'] != 'comment' && $row['type'] != 'pagebreak') {
                    if ($row['number_of_options'] == 0 && $row['type'] == 'open') {
                        $worksheet->setCellValueByColumnAndRow(
                            $column,
                            $line,
                            api_html_entity_decode(
                                strip_tags($row['survey_question']),
                                ENT_QUOTES
                            )
                        );
                        $column++;
                    } else {
                        for ($ii = 0; $ii < $row['number_of_options']; $ii++) {
                            $worksheet->setCellValueByColumnAndRow(
                                $column,
                                $line,
                                api_html_entity_decode(
                                    strip_tags($row['survey_question']),
                                    ENT_QUOTES
                                )
                            );
                            $column++;
                        }
                    }
                }
            }
        }

        $line++;
        $column = 1;
        // Show extra field values
        if ($display_extra_user_fields) {
            // Show the fields names for user fields
            foreach ($extra_user_fields as & $field) {
                $worksheet->setCellValueByColumnAndRow(
                    $column,
                    $line,
                    api_html_entity_decode(strip_tags($field[3]), ENT_QUOTES)
                );
                $column++;
            }
        }

        // Getting all the questions and options (second line)
        $sql = "SELECT
                    survey_question.question_id, 
                    survey_question.survey_id, 
                    survey_question.survey_question, 
                    survey_question.display, 
                    survey_question.sort, 
                    survey_question.type,
                    survey_question_option.question_option_id, 
                    survey_question_option.option_text, 
                    survey_question_option.sort as option_sort
				FROM $table_survey_question survey_question
				LEFT JOIN $table_survey_question_option survey_question_option
				ON 
				    survey_question.question_id = survey_question_option.question_id AND 
				    survey_question_option.c_id = $course_id
				WHERE 
				    survey_question.survey_id = $surveyId AND
				    survey_question.c_id = $course_id
				ORDER BY survey_question.sort ASC, survey_question_option.sort ASC";
        $result = Database::query($sql);
        $possible_answers = array();
        $possible_answers_type = array();
        while ($row = Database::fetch_array($result)) {
            // We show the options if
            // 1. there is no question filter and the export button has not been clicked
            // 2. there is a quesiton filter but the question is selected for display
            if (!isset($_POST['submit_question_filter']) ||
                (isset($_POST['questions_filter']) && is_array($_POST['questions_filter']) &&
                in_array($row['question_id'], $_POST['questions_filter']))
            ) {
                // We do not show comment and pagebreak question types
                if ($row['type'] != 'comment' && $row['type'] != 'pagebreak') {
                    $worksheet->setCellValueByColumnAndRow(
                        $column,
                        $line,
                        api_html_entity_decode(
                            strip_tags($row['option_text']),
                            ENT_QUOTES
                        )
                    );
                    $possible_answers[$row['question_id']][$row['question_option_id']] = $row['question_option_id'];
                    $possible_answers_type[$row['question_id']] = $row['type'];
                    $column++;
                }
            }
        }

        // Getting all the answers of the users
        $line++;
        $column = 0;
        $old_user = '';
        $answers_of_user = array();
        $sql = "SELECT * FROM $table_survey_answer
                WHERE c_id = $course_id AND survey_id = $surveyId";
        if ($user_id != 0) {
            $sql .= " AND user='".intval($user_id)."' ";
        }
        $sql .= " ORDER BY user ASC";

        $open_question_iterator = 1;
        $result = Database::query($sql);
        while ($row = Database::fetch_array($result)) {
            if ($old_user != $row['user'] && $old_user != '') {
                $return = self::export_complete_report_row_xls(
                    $survey_data,
                    $possible_answers,
                    $answers_of_user,
                    $old_user,
                    true
                );
                foreach ($return as $elem) {
                    $worksheet->setCellValueByColumnAndRow($column, $line, $elem);
                    $column++;
                }
                $answers_of_user = array();
                $line++;
                $column = 0;
            }
            if ($possible_answers_type[$row['question_id']] == 'open') {
                $temp_id = 'open'.$open_question_iterator;
                $answers_of_user[$row['question_id']][$temp_id] = $row;
                $open_question_iterator++;
            } else {
                $answers_of_user[$row['question_id']][$row['option_id']] = $row;
            }
            $old_user = $row['user'];
        }

        $return = self::export_complete_report_row_xls(
            $survey_data,
            $possible_answers,
            $answers_of_user,
            $old_user,
            true
        );

        // this is to display the last user
        foreach ($return as $elem) {

The expression $return of type string is not traversable.

            $worksheet->setCellValueByColumnAndRow($column, $line, $elem);
            $column++;
        }

        $file = api_get_path(SYS_ARCHIVE_PATH).api_replace_dangerous_char($filename);
        $writer = new PHPExcel_Writer_Excel2007($spreadsheet);
        $writer->save($file);
        DocumentManager::file_send_for_download($file, true, $filename);

        return null;
    }

    /**
     * Add a line to the csv file
     *
     * @param array Possible answers
     * @param array User's answers
     * @param mixed User ID or user details as string - Used as a string in the result string
     * @param boolean Whether to display user fields or not
     * @return string One line of the csv file
     */

The doc comment User's at position 0 could not be parsed: Unknown type name 'User's' at position 0 in User's.

    public static function export_complete_report_row_xls(
        $survey_data,
        $possible_options,
        $answers_of_user,
        $user,
        $display_extra_user_fields = false
    ) {
        $return = array();
        if ($survey_data['anonymous'] == 0) {
            if (intval($user) !== 0) {
                $userInfo = api_get_user_info($user);
                if ($userInfo) {

The expression $userInfo of type array is implicitly converted to a boolean; are you sure this is intended? If so, consider using ! empty($expr) instead to make it clear that you intend to check for an array without elements.

                    $user_displayed = $userInfo['complete_name_with_username'];
                } else {
                    $user_displayed = '-';
                }
                $return[] = $user_displayed;
            } else {
                $return[] = $user;
            }
        } else {
            $return[] = '-'; // The user column
        }

        if ($display_extra_user_fields) {
            //show user fields data, if any, for this user
            $user_fields_values = UserManager::get_extra_user_data(
                intval($user),
                false,
                false,
                false,
                true
            );
            foreach ($user_fields_values as $value) {
                $return[] = api_html_entity_decode(strip_tags($value), ENT_QUOTES);
            }
        }

        if (is_array($possible_options)) {
            foreach ($possible_options as $question_id => & $possible_option) {
                if (is_array($possible_option) && count($possible_option) > 0) {
                    foreach ($possible_option as $option_id => & $value) {
                        $my_answers_of_user = isset($answers_of_user[$question_id])
                            ? $answers_of_user[$question_id]
                            : [];
                        $key = array_keys($my_answers_of_user);
                        if (isset($key[0]) && substr($key[0], 0, 4) == 'open') {
                            $return[] = api_html_entity_decode(
                                strip_tags($answers_of_user[$question_id][$key[0]]['option_id']),
                                ENT_QUOTES
                            );
                        } elseif (!empty($answers_of_user[$question_id][$option_id])) {
                            if ($answers_of_user[$question_id][$option_id]['value'] != 0) {
                                $return[] = $answers_of_user[$question_id][$option_id]['value'];
                            } else {
                                $return[] = 'v';
                            }
                        } else {
                            $return[] = '';
                        }
                    }
                }
            }
        }

        return $return;

The expression return $return returns the type array|string[] which is incompatible with the documented return type string.

    }

    /**
     * This function displays the comparative report which
     * allows you to compare two questions
     * A comparative report creates a table where one question
     * is on the x axis and a second question is on the y axis.
     * In the intersection is the number of people who have
     * answered positive on both options.
     *
     * @return string HTML code
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007
     */
    public static function display_comparative_report()
    {
        // Allowed question types for comparative report
        $allowed_question_types = array(
            'yesno',
            'multiplechoice',
            'multipleresponse',
            'dropdown',
            'percentage',
            'score'
        );

        $surveyId = isset($_GET['survey_id']) ? (int) $_GET['survey_id'] : 0;

        // Getting all the questions
        $questions = SurveyManager::get_questions($surveyId);

        // Actions bar
        echo '<div class="actions">';
        echo '<a href="'.api_get_path(WEB_CODE_PATH).'survey/reporting.php?survey_id='.$surveyId.'&'.api_get_cidreq()
            .'">'
            .Display::return_icon(
                'back.png',
                get_lang('BackTo').' '.get_lang('ReportingOverview'),
                [],
                ICON_SIZE_MEDIUM
            )
            .'</a>';
        echo '</div>';

        // Displaying an information message that only the questions with predefined answers can be used in a comparative report
        echo Display::return_message(get_lang('OnlyQuestionsWithPredefinedAnswers'), 'normal', false);

        $xAxis = isset($_GET['xaxis']) ? Security::remove_XSS($_GET['xaxis']) : '';
        $yAxis = isset($_GET['yaxis']) ? Security::remove_XSS($_GET['yaxis']) : '';

        $url = api_get_self().'?'.api_get_cidreq().'&action='.Security::remove_XSS($_GET['action'])
            .'&survey_id='.$surveyId.'&xaxis='.$xAxis.'&y='.$yAxis;

        $form = new FormValidator('compare', 'get', $url);
        $form->addHidden('action', Security::remove_XSS($_GET['action']));
        $form->addHidden('survey_id', $surveyId);
        $optionsX = ['----'];
        $optionsY = ['----'];
        $defaults = [];
        foreach ($questions as $key => & $question) {
            if (is_array($allowed_question_types)) {
                if (in_array($question['type'], $allowed_question_types)) {
                    //echo '<option value="'.$question['question_id'].'"';
                    if (isset($_GET['xaxis']) && $_GET['xaxis'] == $question['question_id']) {
                        $defaults['xaxis'] = $question['question_id'];
                    }

                    if (isset($_GET['yaxis']) && $_GET['yaxis'] == $question['question_id']) {
                        $defaults['yaxis'] = $question['question_id'];
                    }

                    $optionsX[$question['question_id']] = api_substr(strip_tags($question['question']), 0, 50);
                    $optionsY[$question['question_id']] = api_substr(strip_tags($question['question']), 0, 50);
                }
            }
        }

        $form->addSelect('xaxis', get_lang('SelectXAxis'), $optionsX);
        $form->addSelect('yaxis', get_lang('SelectYAxis'), $optionsY);

        $form->addButtonSearch(get_lang('CompareQuestions'));
        $form->setDefaults($defaults);
        $form->display();

        // Getting all the information of the x axis
        if (is_numeric($xAxis)) {
            $question_x = SurveyManager::get_question($xAxis);
        }

        // Getting all the information of the y axis
        if (is_numeric($yAxis)) {
            $question_y = SurveyManager::get_question($yAxis);
        }

        if (is_numeric($xAxis) && is_numeric($yAxis)) {
            // Getting the answers of the two questions
            $answers_x = self::get_answers_of_question_by_user($surveyId, $xAxis);
            $answers_y = self::get_answers_of_question_by_user($surveyId, $yAxis);

            // Displaying the table
            $tableHtml = '<table border="1" class="data_table">';
            $xOptions = array();
            // The header
            $tableHtml .= '<tr>';
            for ($ii = 0; $ii <= count($question_x['answers']); $ii++) {

The variable $question_x does not seem to be defined for all execution paths leading up to this point.

It seems like you are calling the size function count() as part of the test condition. You might want to compute the size beforehand, and not on each iteration.

                if ($ii == 0) {
                    $tableHtml .= '<th>&nbsp;</th>';
                } else {
                    if ($question_x['type'] == 'score') {
                        for ($x = 1; $x <= $question_x['maximum_score']; $x++) {
                            $tableHtml .= '<th>'.$question_x['answers'][($ii - 1)].'<br />'.$x.'</th>';
                        }
                        $x = '';
                    } else {
                        $tableHtml .= '<th>'.$question_x['answers'][($ii - 1)].'</th>';
                    }
                    $optionText = strip_tags($question_x['answers'][$ii - 1]);
                    $optionText = html_entity_decode($optionText);
                    array_push($xOptions, trim($optionText));
                }
            }
            $tableHtml .= '</tr>';
            $chartData = array();
            // The main part
            for ($ij = 0; $ij < count($question_y['answers']); $ij++) {

It seems like you are calling the size function count() as part of the test condition. You might want to compute the size beforehand, and not on each iteration.

The variable $question_y does not seem to be defined for all execution paths leading up to this point.

                $currentYQuestion = strip_tags($question_y['answers'][$ij]);
                $currentYQuestion = html_entity_decode($currentYQuestion);
                // The Y axis is a scoring question type so we have more rows than the options (actually options * maximum score)
                if ($question_y['type'] == 'score') {
                    for ($y = 1; $y <= $question_y['maximum_score']; $y++) {
                        $tableHtml .= '<tr>';
                        for ($ii = 0; $ii <= count($question_x['answers']); $ii++) {

It seems like you are calling the size function count() as part of the test condition. You might want to compute the size beforehand, and not on each iteration.

                            if ($question_x['type'] == 'score') {
                                for ($x = 1; $x <= $question_x['maximum_score']; $x++) {
                                    if ($ii == 0) {
                                        $tableHtml .= '<th>'.$question_y['answers'][($ij)].' '.$y.'</th>';
                                        break;
                                    } else {
                                        $tableHtml .= '<td align="center">';
                                        $votes = self::comparative_check(
                                            $answers_x,
                                            $answers_y,
                                            $question_x['answersid'][($ii - 1)],
                                            $question_y['answersid'][($ij)],
                                            $x,
                                            $y
                                        );
                                        $tableHtml .= $votes;
                                        array_push(
                                            $chartData,
                                            array(
                                                'serie' => array($currentYQuestion, $xOptions[$ii - 1]),
                                                'option' => $x,
                                                'votes' => $votes
                                            )
                                        );
                                        $tableHtml .= '</td>';
                                    }
                                }
                            } else {
                                if ($ii == 0) {
                                    $tableHtml .= '<th>'.$question_y['answers'][$ij].' '.$y.'</th>';
                                } else {
                                    $tableHtml .= '<td align="center">';
                                    $votes = self::comparative_check(
                                        $answers_x,
                                        $answers_y,
                                        $question_x['answersid'][($ii - 1)],
                                        $question_y['answersid'][($ij)],
                                        0,
                                        $y
                                    );
                                    $tableHtml .= $votes;
                                    array_push(
                                        $chartData,
                                        array(
                                            'serie' => array($currentYQuestion, $xOptions[$ii - 1]),
                                            'option' => $y,
                                            'votes' => $votes
                                        )
                                    );
                                    $tableHtml .= '</td>';
                                }
                            }
                        }
                        $tableHtml .= '</tr>';
                    }
                } else {
                    // The Y axis is NOT a score question type so the number of rows = the number of options
                    $tableHtml .= '<tr>';
                    for ($ii = 0; $ii <= count($question_x['answers']); $ii++) {

It seems like you are calling the size function count() as part of the test condition. You might want to compute the size beforehand, and not on each iteration.

                        if ($question_x['type'] == 'score') {
                            for ($x = 1; $x <= $question_x['maximum_score']; $x++) {
                                if ($ii == 0) {
                                    $tableHtml .= '<th>'.$question_y['answers'][$ij].'</th>';
                                    break;
                                } else {
                                    $tableHtml .= '<td align="center">';
                                    $votes = self::comparative_check(
                                        $answers_x,
                                        $answers_y,
                                        $question_x['answersid'][($ii - 1)],
                                        $question_y['answersid'][($ij)],
                                        $x,
                                        0
                                    );
                                    $tableHtml .= $votes;
                                    array_push(
                                        $chartData,
                                        array(
                                            'serie' => array($currentYQuestion, $xOptions[$ii - 1]),
                                            'option' => $x,
                                            'votes' => $votes
                                        )
                                    );
                                    $tableHtml .= '</td>';
                                }
                            }
                        } else {
                            if ($ii == 0) {
                                $tableHtml .= '<th>'.$question_y['answers'][($ij)].'</th>';
                            } else {
                                $tableHtml .= '<td align="center">';
                                $votes = self::comparative_check(
                                    $answers_x,
                                    $answers_y,
                                    $question_x['answersid'][($ii - 1)],
                                    $question_y['answersid'][($ij)]
                                );
                                $tableHtml .= $votes;
                                array_push(
                                    $chartData,
                                    array(
                                        'serie' => $xOptions[$ii - 1],
                                        'option' => $currentYQuestion,
                                        'votes' => $votes
                                    )
                                );
                                $tableHtml .= '</td>';
                            }
                        }
                    }
                    $tableHtml .= '</tr>';
                }
            }
            $tableHtml .= '</table>';
            echo '<div id="chartContainer" class="col-md-12">';
            echo self::drawChart($chartData, true);
            echo '</div>';
            echo $tableHtml;
        }
    }

    /**
     * Get all the answers of a question grouped by user
     *
     * @param integer $survey_id Survey ID
     * @param integer $question_id Question ID
     * @return array Array containing all answers of all users, grouped by user
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007 - Updated March 2008
     */
    public static function get_answers_of_question_by_user($survey_id, $question_id)
    {
        $course_id = api_get_course_int_id();
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);

        $sql = "SELECT * FROM $table_survey_answer
                WHERE 
                  c_id = $course_id AND 
                  survey_id='".intval($survey_id)."' AND 
                  question_id='".intval($question_id)."'
                ORDER BY USER ASC";
        $result = Database::query($sql);
        $return = [];
        while ($row = Database::fetch_array($result)) {
            if ($row['value'] == 0) {
                $return[$row['user']][] = $row['option_id'];
            } else {
                $return[$row['user']][] = $row['option_id'].'*'.$row['value'];
            }
        }

        return $return;
    }

    /**
     * Count the number of users who answer positively on both options
     *
     * @param array All answers of the x axis
     * @param array All answers of the y axis
     * @param integer x axis value (= the option_id of the first question)
     * @param integer y axis value (= the option_id of the second question)
     * @return integer Number of users who have answered positively to both options
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version February 2007
     */
    public static function comparative_check(
        $answers_x,
        $answers_y,
        $option_x,
        $option_y,
        $value_x = 0,
        $value_y = 0
    ) {
        if ($value_x == 0) {
            $check_x = $option_x;
        } else {
            $check_x = $option_x.'*'.$value_x;
        }
        if ($value_y == 0) {
            $check_y = $option_y;
        } else {
            $check_y = $option_y.'*'.$value_y;
        }

        $counter = 0;
        if (is_array($answers_x)) {
            foreach ($answers_x as $user => & $answers) {
                // Check if the user has given $option_x as answer
                if (in_array($check_x, $answers)) {
                    // Check if the user has given $option_y as an answer
                    if (!is_null($answers_y[$user]) &&
                        in_array($check_y, $answers_y[$user])
                    ) {
                        $counter++;
                    }
                }
            }
        }

        return $counter;
    }

    /**
     * Get all the information about the invitations of a certain survey
     *
     * @return array Lines of invitation [user, code, date, empty element]
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     *
     * @todo use survey_id parameter instead of $_GET
     */
    public static function get_survey_invitations_data()
    {
        $course_id = api_get_course_int_id();
        // Database table definition
        $table_survey_invitation = Database::get_course_table(TABLE_SURVEY_INVITATION);
        $table_user = Database::get_main_table(TABLE_MAIN_USER);

        $sql = "SELECT
					survey_invitation.user as col1,
					survey_invitation.invitation_code as col2,
					survey_invitation.invitation_date as col3,
					'' as col4
                FROM $table_survey_invitation survey_invitation
                LEFT JOIN $table_user user
                ON survey_invitation.user = user.user_id
                WHERE
                    survey_invitation.c_id = $course_id AND
                    survey_invitation.survey_id = '".intval($_GET['survey_id'])."' AND
                    session_id='".api_get_session_id()."'  ";
        $res = Database::query($sql);
        $data = [];
        while ($row = Database::fetch_array($res)) {
            $data[] = $row;
        }

        return $data;
    }

    /**
     * Get the total number of survey invitations for a given survey (through $_GET['survey_id'])
     *
     * @return integer Total number of survey invitations
     *
     * @todo use survey_id parameter instead of $_GET
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function get_number_of_survey_invitations()
    {
        $course_id = api_get_course_int_id();

        // Database table definition
        $table = Database::get_course_table(TABLE_SURVEY_INVITATION);

        $sql = "SELECT count(user) AS total
		        FROM $table
		        WHERE
                    c_id = $course_id AND
                    survey_id='".intval($_GET['survey_id'])."' AND
                    session_id='".api_get_session_id()."' ";
        $res = Database::query($sql);
        $row = Database::fetch_array($res, 'ASSOC');

        return $row['total'];
    }

    /**
     * Save the invitation mail
     *
     * @param string Text of the e-mail
     * @param integer Whether the mail contents are for invite mail (0, default) or reminder mail (1)
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function save_invite_mail($mailtext, $mail_subject, $reminder = 0)
    {
        $course_id = api_get_course_int_id();
        // Database table definition
        $table_survey = Database::get_course_table(TABLE_SURVEY);

        // Reminder or not
        if ($reminder == 0) {
            $mail_field = 'invite_mail';
        } else {
            $mail_field = 'reminder_mail';
        }

        $sql = "UPDATE $table_survey SET
		        mail_subject='".Database::escape_string($mail_subject)."',
		        $mail_field = '".Database::escape_string($mailtext)."'
		        WHERE c_id = $course_id AND survey_id = '".intval($_GET['survey_id'])."'";
        Database::query($sql);
    }

    /**
     * This function saves all the invitations of course users
     * and additional users in the database
     * and sends the invitations by email
     *
     * @param $users_array Users $array array can be both a list of course uids AND a list of additional emailaddresses
     * @param $invitation_title Title $string of the invitation, used as the title of the mail
     * @param $invitation_text Text $string of the invitation, used as the text of the mail.
     *                         The text has to contain a **link** string or this will automatically be added to the end
     * @param int $reminder
     * @param bool $sendmail
     * @param int $remindUnAnswered
     * @return int
     * @internal param
     * @internal param
     * @internal param
     *                 The text has to contain a **link** string or this will automatically be added to the end
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @author Julio Montoya - Adding auto-generated link support
     * @version January 2007
     */
    public static function saveInvitations(
        $users_array,
        $invitation_title,
        $invitation_text,
        $reminder = 0,
        $sendmail = false,
        $remindUnAnswered = 0
    ) {
        if (!is_array($users_array)) {
            // Should not happen

            return 0;
        }

        // Getting the survey information
        $survey_data = SurveyManager::get_survey($_GET['survey_id']);
        $survey_invitations = self::get_invitations($survey_data['survey_code']);
        $already_invited = self::get_invited_users($survey_data['code']);

        // Remind unanswered is a special version of remind all reminder
        $exclude_users = array();
        if ($remindUnAnswered == 1) { // Remind only unanswered users
            $reminder = 1;
            $exclude_users = SurveyManager::get_people_who_filled_survey($_GET['survey_id']);
        }

        $counter = 0; // Nr of invitations "sent" (if sendmail option)
        $course_id = api_get_course_int_id();
        $session_id = api_get_session_id();
        $result = CourseManager::separateUsersGroups($users_array);

        $groupList = $result['groups'];
        $users_array = $result['users'];

        foreach ($groupList as $groupId) {
            $userGroupList = GroupManager::getStudents($groupId);
            $userGroupIdList = array_column($userGroupList, 'user_id');
            $users_array = array_merge($users_array, $userGroupIdList);

            $params = array(
                'c_id' => $course_id,
                'session_id' => $session_id,
                'group_id' => $groupId,
                'survey_code' => $survey_data['code']
            );

            $invitationExists = self::invitationExists(
                $course_id,
                $session_id,
                $groupId,
                $survey_data['code']
            );
            if (empty($invitationExists)) {
                self::save_invitation($params);
            }
        }

        $users_array = array_unique($users_array);

        foreach ($users_array as $key => $value) {
            if (!isset($value) || $value == '') {
                continue;
            }

            // Skip user if reminding only unanswered people
            if (in_array($value, $exclude_users)) {
                continue;
            }

            // Get the unique invitation code if we already have it
            if ($reminder == 1 && array_key_exists($value, $survey_invitations)) {
                $invitation_code = $survey_invitations[$value]['invitation_code'];
            } else {
                $invitation_code = md5($value.microtime());
            }
            $new_user = false; // User not already invited
            // Store the invitation if user_id not in $already_invited['course_users'] OR email is not in $already_invited['additional_users']
            $addit_users_array = isset($already_invited['additional_users']) && !empty($already_invited['additional_users'])
                    ? explode(';', $already_invited['additional_users'])
                    : array();
            $my_alredy_invited = $already_invited['course_users'] == null ? array() : $already_invited['course_users'];
            if ((is_numeric($value) && !in_array($value, $my_alredy_invited)) ||
                (!is_numeric($value) && !in_array($value, $addit_users_array))
            ) {
                $new_user = true;
                if (!array_key_exists($value, $survey_invitations)) {
                    $params = array(
                        'c_id' => $course_id,
                        'session_id' => $session_id,
                        'user' => $value,
                        'survey_code' => $survey_data['code'],
                        'invitation_code' => $invitation_code,
                        'invitation_date' => api_get_utc_datetime()
                    );
                    self::save_invitation($params);
                }
            }

            // Send the email if checkboxed
            if (($new_user || $reminder == 1) && $sendmail) {
                // Make a change for absolute url
                if (isset($invitation_text)) {
                    $invitation_text = api_html_entity_decode($invitation_text, ENT_QUOTES);
                    $invitation_text = str_replace('src="../../', 'src="'.api_get_path(WEB_PATH), $invitation_text);
                    $invitation_text = trim(stripslashes($invitation_text));
                }
                self::send_invitation_mail(
                    $value,
                    $invitation_code,
                    $invitation_title,
                    $invitation_text
                );
                $counter++;
            }
        }

        return $counter; // Number of invitations sent
    }

    /**
     * @param $params
     * @return bool|int
     */
    public static function save_invitation($params)
    {
        // Database table to store the invitations data
        $table = Database::get_course_table(TABLE_SURVEY_INVITATION);
        if (!empty($params['c_id']) &&
            (!empty($params['user']) || !empty($params['group_id'])) &&
            !empty($params['survey_code'])
        ) {
            $insertId = Database::insert($table, $params);
            if ($insertId) {

The expression $insertId of type integer|false is loosely compared to true; this is ambiguous if the integer can be 0. You might want to explicitly use !== false instead.

                $sql = "UPDATE $table 
                        SET survey_invitation_id = $insertId
                        WHERE iid = $insertId";
                Database::query($sql);
            }

            return $insertId;
        }

        return false;
    }

    /**
     * @param int $courseId
     * @param int $sessionId
     * @param int $groupId
     * @param string $surveyCode
     * @return int
     */
    public static function invitationExists($courseId, $sessionId, $groupId, $surveyCode)
    {
        $table = Database::get_course_table(TABLE_SURVEY_INVITATION);
        $courseId = intval($courseId);
        $sessionId = intval($sessionId);
        $groupId = intval($groupId);
        $surveyCode = Database::escape_string($surveyCode);

        $sql = "SELECT survey_invitation_id FROM $table
                WHERE
                    c_id = $courseId AND
                    session_id = $sessionId AND
                    group_id = $groupId AND
                    survey_code = '$surveyCode'
                ";
        $result = Database::query($sql);

        return Database::num_rows($result);
    }

    /**
     * Send the invitation by mail.
     *
     * @param int invitedUser - the userId (course user) or emailaddress of additional user
     * $param string $invitation_code - the unique invitation code for the URL
     * @return void
     */
    public static function send_invitation_mail(
        $invitedUser,
        $invitation_code,
        $invitation_title,
        $invitation_text
    ) {
        $_user = api_get_user_info();
        $_course = api_get_course_info();

        // Replacing the **link** part with a valid link for the user
        $survey_link = api_get_path(WEB_CODE_PATH).'survey/fillsurvey.php?course='.$_course['code'].'&invitationcode='
            .$invitation_code;
        $text_link = '<a href="'.$survey_link.'">'.get_lang('ClickHereToAnswerTheSurvey')."</a><br />\r\n<br />\r\n"
            .get_lang('OrCopyPasteTheFollowingUrl')." <br />\r\n ".$survey_link;

        $replace_count = 0;
        $full_invitation_text = api_str_ireplace('**link**', $text_link, $invitation_text, $replace_count);
        if ($replace_count < 1) {
            $full_invitation_text = $full_invitation_text."<br />\r\n<br />\r\n".$text_link;
        }

        // Sending the mail
        $sender_name = api_get_person_name($_user['firstName'], $_user['lastName'], null, PERSON_NAME_EMAIL_ADDRESS);
        $sender_email = $_user['mail'];
        $sender_user_id = api_get_user_id();

        $replyto = array();
        if (api_get_setting('survey_email_sender_noreply') == 'noreply') {
            $noreply = api_get_setting('noreply_email_address');
            if (!empty($noreply)) {
                $replyto['Reply-to'] = $noreply;
                $sender_name = $noreply;
                $sender_email = $noreply;
                $sender_user_id = null;
            }
        }

        // Optionally: finding the e-mail of the course user
        if (is_numeric($invitedUser)) {
            MessageManager::send_message(
                $invitedUser,
                $invitation_title,
                $full_invitation_text,
                [],
                [],
                null,
                null,
                null,
                null,
                $sender_user_id
            );
        } else {
            /** @todo check if the address is a valid email */
            $recipient_email = $invitedUser;
            @api_mail_html(

It seems like you do not handle an error condition for api_mail_html(). This can introduce security issues, and is generally not recommended.

                '',
                $recipient_email,
                $invitation_title,
                $full_invitation_text,
                $sender_name,
                $sender_email,
                $replyto
            );
        }
    }

    /**
     * This function recalculates the number of users who have been invited and updates the survey table with this
     * value.
     *
     * @param string Survey code
     * @param int $courseId
     * @param int $sessionId
     * @return int
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function update_count_invited($survey_code, $courseId = 0, $sessionId = 0)
    {
        $courseId = $courseId ?: api_get_course_int_id();
        $sessionId = $sessionId ?: api_get_session_id();
        $sessionCondition = api_get_session_condition($sessionId);

        // Database table definition
        $table_survey_invitation = Database::get_course_table(TABLE_SURVEY_INVITATION);
        $table_survey = Database::get_course_table(TABLE_SURVEY);

        // Counting the number of people that are invited
        $sql = "SELECT count(user) as total
                FROM $table_survey_invitation
		        WHERE
		            c_id = $courseId AND
		            survey_code = '".Database::escape_string($survey_code)."' AND
		            user <> ''
		            $sessionCondition
                ";
        $result = Database::query($sql);
        $row = Database::fetch_array($result);
        $total_invited = $row['total'];

        // Updating the field in the survey table
        $sql = "UPDATE $table_survey
		        SET invited = '".Database::escape_string($total_invited)."'
		        WHERE
		            c_id = $courseId AND
		            code = '".Database::escape_string($survey_code)."'
		            $sessionCondition
                ";
        Database::query($sql);

        return $total_invited;
    }

    /**
     * This function gets all the invited users for a given survey code.
     *
     * @param string Survey code
     * @param string optional - course database
     * @return array Array containing the course users and additional users (non course users)
     *
     * @todo consider making $defaults['additional_users'] also an array
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @author Julio Montoya, adding c_id fixes - Dec 2012
     * @version January 2007
     */
    public static function get_invited_users($survey_code, $course_code = '', $session_id = 0)
    {
        if (!empty($course_code)) {
            $course_info = api_get_course_info($course_code);
            $course_id = $course_info['real_id'];
        } else {
            $course_id = api_get_course_int_id();
        }

        if (empty($session_id)) {
            $session_id = api_get_session_id();
        }

        $table_survey_invitation = Database::get_course_table(TABLE_SURVEY_INVITATION);
        $table_user = Database::get_main_table(TABLE_MAIN_USER);

        // Selecting all the invitations of this survey AND the additional emailaddresses (the left join)
        $order_clause = api_sort_by_first_name() ? ' ORDER BY firstname, lastname' : ' ORDER BY lastname, firstname';
        $sql = "SELECT user, group_id
				FROM $table_survey_invitation as table_invitation
				WHERE
				    table_invitation.c_id = $course_id AND
                    survey_code='".Database::escape_string($survey_code)."' AND
                    session_id = $session_id
                ";

        $defaults = array();
        $defaults['course_users'] = array();
        $defaults['additional_users'] = array(); // Textarea
        $defaults['users'] = array(); // user and groups

        $result = Database::query($sql);
        while ($row = Database::fetch_array($result)) {
            if (is_numeric($row['user'])) {
                $defaults['course_users'][] = $row['user'];
                $defaults['users'][] = 'USER:'.$row['user'];
            } else {
                if (!empty($row['user'])) {
                    $defaults['additional_users'][] = $row['user'];
                }
            }

            if (isset($row['group_id']) && !empty($row['group_id'])) {
                $defaults['users'][] = 'GROUP:'.$row['group_id'];
            }
        }

        if (!empty($defaults['course_users'])) {
            $user_ids = implode("','", $defaults['course_users']);
            $sql = "SELECT user_id FROM $table_user WHERE user_id IN ('$user_ids') $order_clause";
            $result = Database::query($sql);
            $fixed_users = array();
            while ($row = Database::fetch_array($result)) {
                $fixed_users[] = $row['user_id'];
            }
            $defaults['course_users'] = $fixed_users;
        }

        if (!empty($defaults['additional_users'])) {
            $defaults['additional_users'] = implode(';', $defaults['additional_users']);
        }

        return $defaults;
    }

    /**
     * Get all the invitations
     *
     * @param string Survey code
     * @return array Database rows matching the survey code
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version September 2007
     */
    public static function get_invitations($survey_code)
    {
        $course_id = api_get_course_int_id();
        $sessionId = api_get_session_id();
        // Database table definition
        $table_survey_invitation = Database::get_course_table(TABLE_SURVEY_INVITATION);

        $sql = "SELECT * FROM $table_survey_invitation
		        WHERE
		            c_id = $course_id AND
                    session_id = $sessionId AND
		            survey_code = '".Database::escape_string($survey_code)."'";
        $result = Database::query($sql);
        $return = array();
        while ($row = Database::fetch_array($result)) {
            $return[$row['user']] = $row;
        }

        return $return;
    }

    /**
     * This function displays the form for searching a survey
     *
     * @return void (direct output)
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     *
     * @todo use quickforms
     * @todo consider moving this to surveymanager.inc.lib.php
     */
    public static function display_survey_search_form()
    {
        $url = api_get_path(WEB_CODE_PATH).'survey/survey_list.php?search=advanced&'.api_get_cidreq();
        $form = new FormValidator('search', 'get', $url);
        $form->addHeader(get_lang('SearchASurvey'));
        $form->addText('keyword_title', get_lang('Title'));
        $form->addText('keyword_code', get_lang('Code'));
        $form->addSelectLanguage('keyword_language', get_lang('Language'));
        $form->addHidden('cidReq', api_get_course_id());
        $form->addButtonSearch(get_lang('Search'), 'do_search');
        $form->display();
    }

    /**
     * Show table only visible by DRH users
     */
    public static function displaySurveyListForDrh()
    {
        $parameters = array();
        $parameters['cidReq'] = api_get_course_id();

        // Create a sortable table with survey-data
        $table = new SortableTable(
            'surveys',
            'get_number_of_surveys',
            'get_survey_data_drh',
            2
        );
        $table->set_additional_parameters($parameters);
        $table->set_header(0, '', false);
        $table->set_header(1, get_lang('SurveyName'));
        $table->set_header(2, get_lang('SurveyCode'));
        $table->set_header(3, get_lang('NumberOfQuestions'));
        $table->set_header(4, get_lang('Author'));
        $table->set_header(5, get_lang('AvailableFrom'));
        $table->set_header(6, get_lang('AvailableUntil'));
        $table->set_header(7, get_lang('Invite'));
        $table->set_header(8, get_lang('Anonymous'));

        if (api_get_configuration_value('allow_mandatory_survey')) {
            $table->set_header(9, get_lang('IsMandatory'));
            $table->set_header(10, get_lang('Modify'), false, 'width="150"');
            $table->set_column_filter(9, 'anonymous_filter');
            $table->set_column_filter(10, 'modify_filter_drh');
        } else {
            $table->set_header(9, get_lang('Modify'), false, 'width="150"');
            $table->set_column_filter(9, 'modify_filter_drh');
        }

        $table->set_column_filter(8, 'anonymous_filter');
        $table->display();
    }

    /**
     * This function displays the sortable table with all the surveys
     *
     * @return void (direct output)
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function display_survey_list()
    {
        $parameters = array();
        $parameters['cidReq'] = api_get_course_id();
        if (isset($_GET['do_search']) && $_GET['do_search']) {
            $message = get_lang('DisplaySearchResults').'<br />';
            $message .= '<a href="'.api_get_self().'?'.api_get_cidreq().'">'.get_lang('DisplayAll').'</a>';
            echo Display::return_message($message, 'normal', false);
        }

        // Create a sortable table with survey-data
        $table = new SortableTable(
            'surveys',
            'get_number_of_surveys',
            'get_survey_data',
            2
        );
        $table->set_additional_parameters($parameters);
        $table->set_header(0, '', false);
        $table->set_header(1, get_lang('SurveyName'));
        $table->set_header(2, get_lang('SurveyCode'));
        $table->set_header(3, get_lang('NumberOfQuestions'));
        $table->set_header(4, get_lang('Author'));
        //$table->set_header(5, get_lang('Language'));
        //$table->set_header(6, get_lang('Shared'));
        $table->set_header(5, get_lang('AvailableFrom'));
        $table->set_header(6, get_lang('AvailableUntil'));
        $table->set_header(7, get_lang('Invite'));
        $table->set_header(8, get_lang('Anonymous'));

        if (api_get_configuration_value('allow_mandatory_survey')) {
            $table->set_header(9, get_lang('IsMandatory'));
            $table->set_header(10, get_lang('Modify'), false, 'width="150"');
            $table->set_column_filter(9, 'anonymous_filter');
            $table->set_column_filter(10, 'modify_filter');
        } else {
            $table->set_header(9, get_lang('Modify'), false, 'width="150"');
            $table->set_column_filter(9, 'modify_filter');
        }

        $table->set_column_filter(8, 'anonymous_filter');
        $table->set_form_actions(array('delete' => get_lang('DeleteSurvey')));
        $table->display();
    }

    /**
     * Survey list for coach
     */
    public static function display_survey_list_for_coach()
    {
        $parameters = array();
        $parameters['cidReq'] = api_get_course_id();
        if (isset($_GET['do_search'])) {
            $message = get_lang('DisplaySearchResults').'<br />';
            $message .= '<a href="'.api_get_self().'?'.api_get_cidreq().'">'.get_lang('DisplayAll').'</a>';
            echo Display::return_message($message, 'normal', false);
        }

        // Create a sortable table with survey-data
        $table = new SortableTable(
            'surveys_coach',
            'get_number_of_surveys_for_coach',
            'get_survey_data_for_coach',
            2
        );
        $table->set_additional_parameters($parameters);
        $table->set_header(0, '', false);
        $table->set_header(1, get_lang('SurveyName'));
        $table->set_header(2, get_lang('SurveyCode'));
        $table->set_header(3, get_lang('NumberOfQuestions'));
        $table->set_header(4, get_lang('Author'));
        //$table->set_header(5, get_lang('Language'));
        //$table->set_header(6, get_lang('Shared'));
        $table->set_header(5, get_lang('AvailableFrom'));
        $table->set_header(6, get_lang('AvailableUntil'));
        $table->set_header(7, get_lang('Invite'));
        $table->set_header(8, get_lang('Anonymous'));

        if (api_get_configuration_value('allow_mandatory_survey')) {
            $table->set_header(9, get_lang('Modify'), false, 'width="130"');
            $table->set_header(10, get_lang('Modify'), false, 'width="130"');
            $table->set_column_filter(9, 'anonymous_filter');
            $table->set_column_filter(10, 'modify_filter_for_coach');
        } else {
            $table->set_header(9, get_lang('Modify'), false, 'width="130"');
            $table->set_column_filter(9, 'modify_filter_for_coach');
        }

        $table->set_column_filter(8, 'anonymous_filter');
        $table->display();
    }

    /**
     * Check if the hide_survey_edition configurations setting is enabled
     * @param string $surveyCode
     * @return bool
     */
    public static function checkHideEditionToolsByCode($surveyCode)
    {
        $hideSurveyEdition = api_get_configuration_value('hide_survey_edition');

        if (false === $hideSurveyEdition) {
            return false;
        }

        if ('*' === $hideSurveyEdition['codes']) {
            return true;
        }

        if (in_array($surveyCode, $hideSurveyEdition['codes'])) {
            return true;
        }

        return false;
    }

    /**
     * This function changes the modify column of the sortable table
     *
     * @param integer $survey_id the id of the survey
     * @param bool $drh
     * @return string html code that are the actions that can be performed on any survey
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function modify_filter($survey_id, $drh = false)
    {
        /** @var CSurvey $survey */
        $survey = Database::getManager()->find('ChamiloCourseBundle:CSurvey', $survey_id);
        $hideSurveyEdition = self::checkHideEditionToolsByCode($survey->getCode());

        if ($hideSurveyEdition) {
            return '';
        }

        if (empty($survey)) {
            return '';
        }

        $survey_id = $survey->getSurveyId();
        $return = '';
        $hideReportingButton = api_get_configuration_value('hide_survey_reporting_button');

        $reportingLink = Display::url(
            Display::return_icon('stats.png', get_lang('Reporting'), [], ICON_SIZE_SMALL),
            api_get_path(WEB_CODE_PATH).'survey/reporting.php?'.api_get_cidreq().'&survey_id='.$survey_id
        );

        if ($drh) {
            return $hideReportingButton ? '-' : $reportingLink;
        }

        // Coach can see that only if the survey is in his session
        if (api_is_allowed_to_edit() ||
            api_is_element_in_the_session(TOOL_SURVEY, $survey_id)
        ) {
            $return .= '<a href="'.api_get_path(WEB_CODE_PATH).'survey/create_new_survey.php?'.api_get_cidreq()
                .'&action=edit&survey_id='.$survey_id.'">'
                .Display::return_icon('edit.png', get_lang('Edit'), '', ICON_SIZE_SMALL)
                .'</a>';
            if (SurveyManager::survey_generation_hash_available()) {
                $return .= Display::url(
                    Display::return_icon('new_link.png', get_lang('GenerateSurveyAccessLink'), '', ICON_SIZE_SMALL),
                    api_get_path(WEB_CODE_PATH).'survey/generate_link.php?survey_id='.$survey_id.'&'.api_get_cidreq()
                );
            }
            $return .= Display::url(
                Display::return_icon('backup.png', get_lang('CopySurvey'), '', ICON_SIZE_SMALL),
                'copy_survey.php?survey_id='.$survey_id.'&'.api_get_cidreq()
            );
            $return .= Display::url(
                Display::return_icon('copy.png', get_lang('DuplicateSurvey'), '', ICON_SIZE_SMALL),
                'survey_list.php?action=copy_survey&survey_id='.$survey_id.'&'.api_get_cidreq()
            );

            $return .= ' <a href="'.api_get_path(WEB_CODE_PATH).'survey/survey_list.php?'.api_get_cidreq()
                .'&action=empty&survey_id='.$survey_id.'" onclick="javascript: if(!confirm(\''
                .addslashes(api_htmlentities(get_lang("EmptySurvey").'?')).'\')) return false;">'
                .Display::return_icon('clean.png', get_lang('EmptySurvey'), '', ICON_SIZE_SMALL)
                .'</a>&nbsp;';
        }
        $return .= '<a href="'.api_get_path(WEB_CODE_PATH).'survey/preview.php?'.api_get_cidreq().'&survey_id='.$survey_id.'">'
            .Display::return_icon('preview_view.png', get_lang('Preview'), '', ICON_SIZE_SMALL)
            .'</a>&nbsp;';
        $return .= '<a href="'.api_get_path(WEB_CODE_PATH).'survey/survey_invite.php?'.api_get_cidreq().'&survey_id='.$survey_id.'">'
            .Display::return_icon('mail_send.png', get_lang('Publish'), '', ICON_SIZE_SMALL)
            .'</a>&nbsp;';
        $return .= $hideReportingButton ? '' : $reportingLink;

        if (api_is_allowed_to_edit() ||
            api_is_element_in_the_session(TOOL_SURVEY, $survey_id)
        ) {
            $return .= '<a href="'.api_get_path(WEB_CODE_PATH).'survey/survey_list.php?'.api_get_cidreq()
                .'&action=delete&survey_id='.$survey_id.'" onclick="javascript: if(!confirm(\''
                .addslashes(api_htmlentities(get_lang("DeleteSurvey").'?', ENT_QUOTES)).'\')) return false;">'
                .Display::return_icon('delete.png', get_lang('Delete'), '', ICON_SIZE_SMALL)
                .'</a>&nbsp;';
        }

        return $return;
    }

    /**
     * @param int $survey_id
     * @return string
     */
    public static function modify_filter_for_coach($survey_id)
    {
        $survey_id = (int) $survey_id;
        $return = '<a href="'.api_get_path(WEB_CODE_PATH).'survey/preview.php?'.api_get_cidreq().'&survey_id='.$survey_id.'">'
            .Display::return_icon('preview_view.png', get_lang('Preview'), '', ICON_SIZE_SMALL).'</a>&nbsp;';
        $return .= '<a href="'.api_get_path(WEB_CODE_PATH).'survey/survey_invite.php?'.api_get_cidreq().'&survey_id='.$survey_id.'">'.
            Display::return_icon('mail_send.png', get_lang('Publish'), '', ICON_SIZE_SMALL)
            .'</a>&nbsp;';
        $return .= '<a href="'.api_get_path(WEB_CODE_PATH).'survey/survey_list.php?'.api_get_cidreq().'&action=empty&survey_id='.$survey_id.'" onclick="javascript: if(!confirm(\''
            .addslashes(api_htmlentities(get_lang("EmptySurvey").'?', ENT_QUOTES)).'\')) return false;">'
            .Display::return_icon('clean.png', get_lang('EmptySurvey'), '', ICON_SIZE_SMALL).'</a>&nbsp;';

        return $return;
    }

    /**
     * Returns "yes" when given parameter is one, "no" for any other value
     * @param integer Whether anonymous or not
     * @return string "Yes" or "No" in the current language
     */
    public static function anonymous_filter($anonymous)
    {
        if ($anonymous == 1) {
            return get_lang('Yes');
        } else {
            return get_lang('No');
        }
    }

    /**
     * This function handles the search restriction for the SQL statements
     *
     * @return string Part of a SQL statement or false on error
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function survey_search_restriction()
    {
        if (isset($_GET['do_search'])) {
            if ($_GET['keyword_title'] != '') {
                $search_term[] = 'title like "%" \''.Database::escape_string($_GET['keyword_title']).'\' "%"';

$search_term was never initialized. Although not strictly required by PHP, it is generally a good practice to add $search_term = array(); before regardless.

            }
            if ($_GET['keyword_code'] != '') {
                $search_term[] = 'code =\''.Database::escape_string($_GET['keyword_code']).'\'';
            }
            if ($_GET['keyword_language'] != '%') {
                $search_term[] = 'lang =\''.Database::escape_string($_GET['keyword_language']).'\'';
            }
            $my_search_term = ($search_term == null) ? array() : $search_term;

The variable $search_term does not seem to be defined for all execution paths leading up to this point.

            $search_restriction = implode(' AND ', $my_search_term);

            return $search_restriction;
        } else {
            return false;

The expression return false returns the type false which is incompatible with the documented return type string.

        }
    }

    /**
     * This function calculates the total number of surveys
     *
     * @return integer Total number of surveys
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version January 2007
     */
    public static function get_number_of_surveys()
    {
        $table_survey = Database::get_course_table(TABLE_SURVEY);
        $course_id = api_get_course_int_id();

        $search_restriction = self::survey_search_restriction();
        if ($search_restriction) {
            $search_restriction = 'WHERE c_id = '.$course_id.' AND '.$search_restriction;
        } else {
            $search_restriction = "WHERE c_id = $course_id";
        }
        $sql = "SELECT count(survey_id) AS total_number_of_items
		        FROM ".$table_survey.' '.$search_restriction;
        $res = Database::query($sql);
        $obj = Database::fetch_object($res);

        return $obj->total_number_of_items;
    }

    /**
     * @return int
     */
    public static function get_number_of_surveys_for_coach()
    {
        $survey_tree = new SurveyTree();

        return count($survey_tree->surveylist);
    }

    /**
     * This function gets all the survey data that is to be displayed in the sortable table
     *
     * @param int $from
     * @param int $number_of_items
     * @param int $column
     * @param string $direction
     * @param bool $isDrh
     * @return array
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @author Julio Montoya <gugli100@gmail.com>, Beeznest - Adding intvals
     * @version January 2007
     */
    public static function get_survey_data(
        $from,
        $number_of_items,
        $column,
        $direction,
        $isDrh = false
    ) {
        $table_survey = Database::get_course_table(TABLE_SURVEY);
        $table_user = Database::get_main_table(TABLE_MAIN_USER);
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $mandatoryAllowed = api_get_configuration_value('allow_mandatory_survey');
        $_user = api_get_user_info();

        // Searching
        $search_restriction = self::survey_search_restriction();
        if ($search_restriction) {
            $search_restriction = ' AND '.$search_restriction;
        }
        $from = intval($from);
        $number_of_items = intval($number_of_items);
        $column = intval($column);
        if (!in_array(strtolower($direction), array('asc', 'desc'))) {
            $direction = 'asc';
        }

        // Condition for the session
        $session_id = api_get_session_id();
        $condition_session = api_get_session_condition($session_id);
        $course_id = api_get_course_int_id();

        $sql = "
            SELECT
                survey.survey_id AS col0,
                survey.title AS col1,
                survey.code AS col2,
                count(survey_question.question_id) AS col3, "
                .(api_is_western_name_order()
                ? "CONCAT(user.firstname, ' ', user.lastname)"
                : "CONCAT(user.lastname, ' ', user.firstname)")
                ."	AS col4,
                survey.avail_from AS col5,
                survey.avail_till AS col6,
                survey.invited AS col7,
                survey.anonymous AS col8,
                survey.survey_id AS col9,
                survey.session_id AS session_id,
                survey.answered,
                survey.invited
            FROM $table_survey survey
            LEFT JOIN $table_survey_question survey_question
            ON (survey.survey_id = survey_question.survey_id AND survey_question.c_id = $course_id)
            LEFT JOIN $table_user user
            ON (survey.author = user.user_id)
            WHERE survey.c_id = $course_id
            $search_restriction
            $condition_session 
            GROUP BY survey.survey_id
            ORDER BY col$column $direction 
            LIMIT $from,$number_of_items
        ";

        $res = Database::query($sql);
        $surveys = array();
        $array = array();
        $efv = new ExtraFieldValue('survey');

        while ($survey = Database::fetch_array($res)) {
            $array[0] = $survey[0];

            if (self::checkHideEditionToolsByCode($survey['col2'])) {
                $array[1] = $survey[1];
            } else {
                $array[1] = Display::url(
                    $survey[1],
                    api_get_path(WEB_CODE_PATH).'survey/survey.php?survey_id='.$survey[0].'&'.api_get_cidreq()
                );
            }

            // Validation when belonging to a session
            $session_img = api_get_session_image($survey['session_id'], $_user['status']);
            $array[2] = $survey[2].$session_img;
            $array[3] = $survey[3];
            $array[4] = $survey[4];
            $array[5] = $survey[5];
            $array[6] = $survey[6];
            $array[7] =
                Display::url(
                    $survey['answered'],
                    api_get_path(WEB_CODE_PATH).'survey/survey_invitation.php?view=answered&survey_id='.$survey[0].'&'
                        .api_get_cidreq()
                ).' / '.
                Display::url(
                    $survey['invited'],
                    api_get_path(WEB_CODE_PATH).'survey/survey_invitation.php?view=invited&survey_id='.$survey[0].'&'
                        .api_get_cidreq()
                );

            $array[8] = $survey[8];

            if ($mandatoryAllowed) {
                $efvMandatory = $efv->get_values_by_handler_and_field_variable(
                    $survey[9],
                    'is_mandatory'
                );

                $array[9] = $efvMandatory ? $efvMandatory['value'] : 0;
                $array[10] = $survey[9];
            } else {
                $array[9] = $survey[9];
            }

            if ($isDrh) {
                $array[1] = $survey[1];
                $array[7] = strip_tags($array[7]);
            }

            $surveys[] = $array;
        }

        return $surveys;
    }

    /**
     * @param $from
     * @param $number_of_items
     * @param $column
     * @param $direction
     * @return array
     */
    public static function get_survey_data_for_coach($from, $number_of_items, $column, $direction)
    {
        $mandatoryAllowed = api_get_configuration_value('allow_mandatory_survey');
        $survey_tree = new SurveyTree();
        //$last_version_surveys = $survey_tree->get_last_children_from_branch($survey_tree->surveylist);
        $last_version_surveys = $survey_tree->surveylist;
        $list = array();
        foreach ($last_version_surveys as & $survey) {
            $list[] = $survey['id'];
        }
        if (count($list) > 0) {
            $list_condition = " AND survey.survey_id IN (".implode(',', $list).") ";
        } else {
            $list_condition = '';
        }

        $from = intval($from);
        $number_of_items = intval($number_of_items);
        $column = intval($column);
        if (!in_array(strtolower($direction), array('asc', 'desc'))) {
            $direction = 'asc';
        }

        $table_survey = Database::get_course_table(TABLE_SURVEY);
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $table_user = Database::get_main_table(TABLE_MAIN_USER);
        $course_id = api_get_course_int_id();
        $efv = new ExtraFieldValue('survey');

        $sql = "
            SELECT 
            survey.survey_id AS col0, 
                survey.title AS col1, 
                survey.code AS col2, 
                count(survey_question.question_id) AS col3, 
        "
            .(api_is_western_name_order()
                ? "CONCAT(user.firstname, ' ', user.lastname)"
                : "CONCAT(user.lastname, ' ', user.firstname)")
            ."	AS col4,
                survey.avail_from AS col5,
                survey.avail_till AS col6,
                CONCAT('<a href=\"survey_invitation.php?view=answered&survey_id=',survey.survey_id,'\">',survey.answered,'</a> / <a href=\"survey_invitation.php?view=invited&survey_id=',survey.survey_id,'\">',survey.invited, '</a>') AS col7,
                survey.anonymous AS col8,
                survey.survey_id AS col9
            FROM $table_survey survey
            LEFT JOIN $table_survey_question survey_question
            ON (survey.survey_id = survey_question.survey_id AND survey.c_id = survey_question.c_id),
            $table_user user
            WHERE survey.author = user.user_id AND survey.c_id = $course_id $list_condition
        ";
        $sql .= " GROUP BY survey.survey_id";
        $sql .= " ORDER BY col$column $direction ";
        $sql .= " LIMIT $from,$number_of_items";

        $res = Database::query($sql);
        $surveys = array();
        while ($survey = Database::fetch_array($res)) {
            if ($mandatoryAllowed) {
                $survey['col10'] = $survey['col9'];
                $efvMandatory = $efv->get_values_by_handler_and_field_variable(
                    $survey['col9'],
                    'is_mandatory'
                );
                $survey['col9'] = $efvMandatory['value'];
            }
            $surveys[] = $survey;
        }

        return $surveys;
    }

    /**
     * Display all the active surveys for the given course user
     *
     * @param int $user_id
     *
     * @author Patrick Cool <patrick.cool@UGent.be>, Ghent University
     * @version April 2007
     */
    public static function getSurveyList($user_id)
    {
        $_course = api_get_course_info();
        $course_id = $_course['real_id'];
        $user_id = intval($user_id);
        $sessionId = api_get_session_id();
        $mandatoryAllowed = api_get_configuration_value('allow_mandatory_survey');

        // Database table definitions
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);
        $table_survey_invitation = Database::get_course_table(TABLE_SURVEY_INVITATION);
        $table_survey = Database::get_course_table(TABLE_SURVEY);

        $sql = "SELECT question_id
                FROM $table_survey_question
                WHERE c_id = $course_id";
        $result = Database::query($sql);

        $all_question_id = array();
        while ($row = Database::fetch_array($result, 'ASSOC')) {
            $all_question_id[] = $row;
        }

        echo '<table id="list-survey" class="table ">';
        echo '<thead>';
        echo '<tr>';
        echo '	<th>'.get_lang('SurveyName').'</th>';
        echo '	<th class="text-center">'.get_lang('Anonymous').'</th>';
        if ($mandatoryAllowed) {
            echo '<th class="text-center">'.get_lang('IsMandatory').'</th>';
        }
        echo '</tr>';
        echo '</thead>';
        echo '<tbody>';

        /** @var \DateTime $now */
        $now = api_get_utc_datetime(null, false, true);

        $sql = "SELECT *
                FROM $table_survey survey 
                INNER JOIN
                $table_survey_invitation survey_invitation
                ON (
                    survey.code = survey_invitation.survey_code AND
                    survey.c_id = survey_invitation.c_id
                    AND survey.session_id = survey_invitation.session_id
                )
				WHERE
                    survey_invitation.user = $user_id AND                    
                    survey.avail_from <= '".$now->format('Y-m-d')."' AND
                    survey.avail_till >= '".$now->format('Y-m-d')."' AND
                    survey.c_id = $course_id AND
                    survey.session_id = $sessionId AND
                    survey_invitation.c_id = $course_id
				";
        $result = Database::query($sql);

        $efv = new ExtraFieldValue('survey');

        while ($row = Database::fetch_array($result, 'ASSOC')) {
            echo '<tr>';
            if ($row['answered'] == 0) {
                echo '<td>';
                echo Display::return_icon(
                    'statistics.png',
                    get_lang('CreateNewSurvey'),
                    array(),
                    ICON_SIZE_TINY
                );
                echo '<a href="'.api_get_path(WEB_CODE_PATH).'survey/fillsurvey.php?course='.$_course['sysCode']
                    .'&invitationcode='.$row['invitation_code'].'&cidReq='.$_course['sysCode'].'">'.$row['title']
                    .'</a></td>';
            } else {
                $isDrhOfCourse = CourseManager::isUserSubscribedInCourseAsDrh(
                    $user_id,
                    $_course
                );
                $icon = Display::return_icon(
                    'statistics_na.png',
                    get_lang('Survey'),
                    array(),
                    ICON_SIZE_TINY
                );
                $showLink = (!api_is_allowed_to_edit(false, true) || $isDrhOfCourse)
                    && $row['visible_results'] != SURVEY_VISIBLE_TUTOR;

                echo '<td>';
                echo $showLink
                    ? Display::url(
                        $icon.PHP_EOL.$row['title'],
                        api_get_path(WEB_CODE_PATH).'survey/reporting.php?'.api_get_cidreq().'&'.http_build_query([
                            'action' => 'questionreport',
                            'survey_id' => $row['survey_id']
                        ])
                    )
                    : $icon.PHP_EOL.$row['title'];
                echo '</td>';
            }
            echo '<td class="text-center">';
            echo ($row['anonymous'] == 1) ? get_lang('Yes') : get_lang('No');
            echo '</td>';
            if ($mandatoryAllowed) {
                $efvMandatory = $efv->get_values_by_handler_and_field_variable(
                    $row['survey_id'],
                    'is_mandatory'
                );
                echo '<td class="text-center">'.($efvMandatory['value'] ? get_lang('Yes') : get_lang('No')).'</td>';
            }

            echo '</tr>';
        }
        echo '</tbody>';
        echo '</table>';
    }

    /**
     * Creates a multi array with the user fields that we can show.
     * We look the visibility with the api_get_setting function
     * The username is always NOT able to change it.
     * @author Julio Montoya Armas <gugli100@gmail.com>, Chamilo: Personality Test modification
     * @return array  array[value_name][name], array[value_name][visibilty]
     */
    public static function make_field_list()
    {
        //	LAST NAME and FIRST NAME
        $field_list_array = array();
        $field_list_array['lastname']['name'] = get_lang('LastName');
        $field_list_array['firstname']['name'] = get_lang('FirstName');

        if (api_get_setting('profile', 'name') != 'true') {
            $field_list_array['firstname']['visibility'] = 0;
            $field_list_array['lastname']['visibility'] = 0;
        } else {
            $field_list_array['firstname']['visibility'] = 1;
            $field_list_array['lastname']['visibility'] = 1;
        }

        $field_list_array['username']['name'] = get_lang('Username');
        $field_list_array['username']['visibility'] = 0;

        //	OFFICIAL CODE
        $field_list_array['official_code']['name'] = get_lang('OfficialCode');

        if (api_get_setting('profile', 'officialcode') != 'true') {
            $field_list_array['official_code']['visibility'] = 1;
        } else {
            $field_list_array['official_code']['visibility'] = 0;
        }

        // EMAIL
        $field_list_array['email']['name'] = get_lang('Email');
        if (api_get_setting('profile', 'email') != 'true') {
            $field_list_array['email']['visibility'] = 1;
        } else {
            $field_list_array['email']['visibility'] = 0;
        }

        // PHONE
        $field_list_array['phone']['name'] = get_lang('Phone');
        if (api_get_setting('profile', 'phone') != 'true') {
            $field_list_array['phone']['visibility'] = 0;
        } else {
            $field_list_array['phone']['visibility'] = 1;
        }
        //	LANGUAGE
        $field_list_array['language']['name'] = get_lang('Language');
        if (api_get_setting('profile', 'language') != 'true') {
            $field_list_array['language']['visibility'] = 0;
        } else {
            $field_list_array['language']['visibility'] = 1;
        }

        // EXTRA FIELDS
        $extra = UserManager::get_extra_fields(0, 50, 5, 'ASC');

        foreach ($extra as $id => $field_details) {
            if ($field_details[6] == 0) {
                continue;
            }
            switch ($field_details[2]) {
                case UserManager::USER_FIELD_TYPE_TEXT:
                    $field_list_array['extra_'.$field_details[1]]['name'] = $field_details[3];
                    if ($field_details[7] == 0) {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 0;
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 1;
                    }
                    break;
                case UserManager::USER_FIELD_TYPE_TEXTAREA:
                    $field_list_array['extra_'.$field_details[1]]['name'] = $field_details[3];
                    if ($field_details[7] == 0) {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 0;
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 1;
                    }
                    break;
                case UserManager::USER_FIELD_TYPE_RADIO:
                    $field_list_array['extra_'.$field_details[1]]['name'] = $field_details[3];
                    if ($field_details[7] == 0) {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 0;
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 1;
                    }
                    break;
                case UserManager::USER_FIELD_TYPE_SELECT:
                    $get_lang_variables = false;
                    if (in_array(
                        $field_details[1],
                        array('mail_notify_message', 'mail_notify_invitation', 'mail_notify_group_message'))
                    ) {
                        $get_lang_variables = true;
                    }

                    if ($get_lang_variables) {
                        $field_list_array['extra_'.$field_details[1]]['name'] = get_lang($field_details[3]);
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['name'] = $field_details[3];
                    }

                    if ($field_details[7] == 0) {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 0;
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 1;
                    }
                    break;
                case UserManager::USER_FIELD_TYPE_SELECT_MULTIPLE:
                    $field_list_array['extra_'.$field_details[1]]['name'] = $field_details[3];
                    if ($field_details[7] == 0) {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 0;
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 1;
                    }
                    break;
                case UserManager::USER_FIELD_TYPE_DATE:
                    $field_list_array['extra_'.$field_details[1]]['name'] = $field_details[3];
                    if ($field_details[7] == 0) {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 0;
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 1;
                    }
                    break;
                case UserManager::USER_FIELD_TYPE_DATETIME:
                    $field_list_array['extra_'.$field_details[1]]['name'] = $field_details[3];
                    if ($field_details[7] == 0) {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 0;
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 1;
                    }
                    break;
                case UserManager::USER_FIELD_TYPE_DOUBLE_SELECT:
                    $field_list_array['extra_'.$field_details[1]]['name'] = $field_details[3];
                    if ($field_details[7] == 0) {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 0;
                    } else {
                        $field_list_array['extra_'.$field_details[1]]['visibility'] = 1;
                    }
                    break;
                case UserManager::USER_FIELD_TYPE_DIVIDER:
                    //$form->addElement('static',$field_details[1], '<br /><strong>'.$field_details[3].'</strong>');
                    break;
            }
        }

        return $field_list_array;
    }

    /**
     * @author Isaac Flores Paz <florespaz@bidsoftperu.com>
     * @param int $user_id User ID
     * @param string $survey_code
     * @param int $user_answer User in survey answer table (user id or anonymous)
     * @return boolean
     */
    public static function show_link_available($user_id, $survey_code, $user_answer)
    {
        $table_survey = Database::get_course_table(TABLE_SURVEY);
        $table_survey_invitation = Database::get_course_table(TABLE_SURVEY_INVITATION);
        $table_survey_answer = Database::get_course_table(TABLE_SURVEY_ANSWER);
        $table_survey_question = Database::get_course_table(TABLE_SURVEY_QUESTION);

        $survey_code = Database::escape_string($survey_code);
        $user_id = intval($user_id);
        $user_answer = Database::escape_string($user_answer);
        $course_id = api_get_course_int_id();

        $sql = 'SELECT COUNT(*) as count
                FROM '.$table_survey_invitation.'
		        WHERE
		            user='.$user_id.' AND
		            survey_code="'.$survey_code.'" AND 
		            answered="1" AND 
		            c_id = '.$course_id;

        $sql2 = 'SELECT COUNT(*) as count 
                 FROM '.$table_survey.' s 
                 INNER JOIN '.$table_survey_question.' q 
                 ON s.survey_id=q.survey_id
				 WHERE 
				    s.code="'.$survey_code.'" AND 
				    q.type NOT IN("pagebreak","comment") AND s.c_id = '.$course_id.' AND q.c_id = '.$course_id.' ';

        $sql3 = 'SELECT COUNT(DISTINCT question_id) as count 
                 FROM '.$table_survey_answer.'
				 WHERE survey_id=(
				    SELECT survey_id FROM '.$table_survey.'
				    WHERE 
				        code = "'.$survey_code.'" AND 
				        c_id = '.$course_id.' 
                    )  AND 
                user="'.$user_answer.'" AND 
                c_id = '.$course_id;

        $result = Database::query($sql);
        $result2 = Database::query($sql2);
        $result3 = Database::query($sql3);

        $row = Database::fetch_array($result, 'ASSOC');
        $row2 = Database::fetch_array($result2, 'ASSOC');
        $row3 = Database::fetch_array($result3, 'ASSOC');

        if ($row['count'] == 1 && $row3['count'] != $row2['count']) {
            return true;
        } else {
            return false;
        }
    }

    /**
     * Display survey question chart
     * @param array $chartData
     * @param boolean $hasSerie Tells if the chart has a serie. False by default
     * @param string $chartContainerId
     * @return string (direct output)
     */
    public static function drawChart(
        $chartData,
        $hasSerie = false,
        $chartContainerId = 'chartContainer'
    ) {
        $htmlChart = '';
        if (api_browser_support("svg")) {
            $htmlChart .= api_get_js("d3/d3.v3.5.4.min.js");
            $htmlChart .= api_get_js("dimple.v2.1.2.min.js").'
            <script>
            var svg = dimple.newSvg("#'.$chartContainerId.'", "100%", 400);
            var data = [';
            $serie = array();
            $order = array();
            foreach ($chartData as $chartDataElement) {
                $htmlChart .= '{"';
                if (!$hasSerie) {
                    $htmlChart .= get_lang("Option").'":"'.$chartDataElement['option'].'", "';
                    array_push($order, $chartDataElement['option']);
                } else {
                    if (!is_array($chartDataElement['serie'])) {
                        $htmlChart .= get_lang("Option").'":"'.$chartDataElement['serie'].'", "'.
                            get_lang("Score").'":"'.$chartDataElement['option'].'", "';
                        array_push($serie, $chartDataElement['serie']);
                    } else {
                        $htmlChart .= get_lang("Serie").'":"'.$chartDataElement['serie'][0].'", "'.
                            get_lang("Option").'":"'.$chartDataElement['serie'][1].'", "'.
                            get_lang("Score").'":"'.$chartDataElement['option'].'", "';
                    }
                }
                $htmlChart .= get_lang("Votes").'":"'.$chartDataElement['votes'].
                    '"},';
            }
            rtrim($htmlChart, ",");
            $htmlChart .= '];
                var myChart = new dimple.chart(svg, data);
                myChart.addMeasureAxis("y", "'.get_lang("Votes").'");';
            if (!$hasSerie) {
                $htmlChart .= 'var xAxisCategory = myChart.addCategoryAxis("x", "'.get_lang("Option").'");
                    xAxisCategory.addOrderRule('.json_encode($order).');
                    myChart.addSeries("'.get_lang("Option").'", dimple.plot.bar);';
            } else {
                if (!is_array($chartDataElement['serie'])) {

The variable $chartDataElement seems to be defined by a foreach iteration on line 3529. Are you sure the iterator is never empty, otherwise this variable is not defined?

                    $serie = array_values(array_unique($serie));
                    $htmlChart .= 'var xAxisCategory = myChart.addCategoryAxis("x", ["'.get_lang("Option").'","'
                        .get_lang("Score").'"]);
                        xAxisCategory.addOrderRule('.json_encode($serie).');
                        xAxisCategory.addGroupOrderRule("'.get_lang("Score").'");
                        myChart.addSeries("'.get_lang("Option").'", dimple.plot.bar);';
                } else {
                    $htmlChart .= 'myChart.addCategoryAxis("x", ["'.get_lang("Option").'","'.get_lang("Score").'"]);
                        myChart.addSeries("'.get_lang("Serie").'", dimple.plot.bar);';
                }
            }
            $htmlChart .= 'myChart.draw();
                </script>';
        }

        return $htmlChart;
    }

    /**
     * Set a flag to the current survey as answered by the current user
     * @param string $surveyCode The survey code
     * @param int $courseId The course ID
     */
    public static function flagSurveyAsAnswered($surveyCode, $courseId)
    {
        $currentUserId = api_get_user_id();
        $flag = sprintf("%s-%s-%d", $courseId, $surveyCode, $currentUserId);

        if (!isset($_SESSION['filled_surveys'])) {
            $_SESSION['filled_surveys'] = array();
        }

        $_SESSION['filled_surveys'][] = $flag;
    }

    /**
     * Check whether a survey was answered by the current user
     * @param string $surveyCode The survey code
     * @param int $courseId The course ID
     * @return boolean
     */
    public static function isSurveyAnsweredFlagged($surveyCode, $courseId)
    {
        $currentUserId = api_get_user_id();
        $flagToCheck = sprintf("%s-%s-%d", $courseId, $surveyCode, $currentUserId);

        if (!isset($_SESSION['filled_surveys'])) {
            return false;
        }

        if (!is_array($_SESSION['filled_surveys'])) {
            return false;
        }

        foreach ($_SESSION['filled_surveys'] as $flag) {
            if ($flagToCheck != $flag) {
                continue;
            }

            return true;
        }

        return false;
    }

    /**
     * Check if the current survey has answers
     *
     * @param int $surveyId
     * @return boolean return true if the survey has answers, false otherwise
     */
    public static function checkIfSurveyHasAnswers($surveyId)
    {
        $tableSurveyAnswer = Database::get_course_table(TABLE_SURVEY_ANSWER);
        $courseId = api_get_course_int_id();
        $surveyId = (int) $surveyId;

        if (empty($courseId) || empty($surveyId)) {
            return false;
        }

        $sql = "SELECT * FROM $tableSurveyAnswer
                WHERE
                    c_id = $courseId AND
                    survey_id = '".$surveyId."'
                ORDER BY answer_id, user ASC";
        $result = Database::query($sql);
        $response = Database::affected_rows($result);

        return $response > 0;
    }
}