chamilo / chamilo-lms

main/inc/lib/course_request.lib.php

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

/**
 * Course request manager.
 *
 * @author José Manuel Abuin Mosquera <chema@cesga.es>, 2010
 * @author Bruno Rubio Gayo <brubio@cesga.es>, 2010
 * Centro de Supercomputacion de Galicia (CESGA)
 * @author Ivan Tcholakov <ivantcholakov@gmail.com> (technical adaptation for Chamilo 1.8.8), 2010
 */
class CourseRequestManager
{
    /**
     * Checks whether a given course code has been already occupied.
     *
     * @param string $wanted_course_code the code to be checked
     *
     * @return bool
     *              Returns TRUE if there is created:
     *              - a course with the same code OR visual_code (visualcode).
     *              - a course request with the same code as the given one, or
     *              Othewise returns FALSE.
     */
    public static function course_code_exists($wanted_course_code)
    {
        if ($code_exists = CourseManager::course_code_exists($wanted_course_code)) {
            return $code_exists;
        }
        $table_course_request = Database::get_main_table(TABLE_MAIN_COURSE_REQUEST);
        $wanted_course_code = Database::escape_string($wanted_course_code);
        $sql = sprintf(
            'SELECT COUNT(id) AS number FROM %s WHERE visual_code = "%s"',
            $table_course_request,
            $wanted_course_code
        );
        $result = Database::fetch_array(Database::query($sql));

        return $result['number'] > 0;
    }

    /**
     * Creates a new course request within the database.
     *
     * @param string $wanted_code     the code for the created in the future course
     * @param string $title
     * @param string $description
     * @param string $category_code
     * @param string $course_language
     * @param string $objectives
     * @param string $target_audience
     * @param int    $user_id
     *
     * @return mixed the database id of the newly created course request or FALSE on failure
     */
    public static function create_course_request(
        $wanted_code,
        $title,
        $description,
        $category_code,
        $course_language,
        $objectives,
        $target_audience,
        $user_id,
        $exemplary_content
    ) {
        $wanted_code = trim($wanted_code);
        $user_id = (int) $user_id;
        $exemplary_content = (bool) $exemplary_content ? 1 : 0;

        if ('' == $wanted_code) {
            return false;
        }

        if (self::course_code_exists($wanted_code)) {
            return false;
        }

        if ($user_id <= 0) {
            return false;
        }

        $user_info = api_get_user_info($user_id);
        if (!is_array($user_info)) {
            return false;
        }

        $tutor_name = api_get_person_name($user_info['firstname'], $user_info['lastname'], null, null, $course_language);

        $request_date = api_get_utc_datetime();
        $status = COURSE_REQUEST_PENDING;
        $info = 0;
        $keys = AddCourse::define_course_keys($wanted_code, '');
        if (!count($keys)) {
            return false;
        }
        $visual_code = $keys['currentCourseCode'];
        $code = $keys['currentCourseId'];
        $db_name = isset($keys['currentCourseDbName']) ? $keys['currentCourseDbName'] : null;
        $directory = $keys['currentCourseRepository'];
        // @todo user entity
        $sql = sprintf(
            'INSERT INTO %s (
                code, user_id, directory, db_name,
                course_language, title, description, category_code,
                tutor_name, visual_code, request_date,
                objetives, target_audience, status, info, exemplary_content)
            VALUES (
                "%s", "%s", "%s", "%s",
                "%s", "%s", "%s", "%s",
                "%s", "%s", "%s",
                "%s", "%s", "%s", "%s", "%s");',
            Database::get_main_table(TABLE_MAIN_COURSE_REQUEST),
            Database::escape_string($code),
            Database::escape_string($user_id),
            Database::escape_string($directory),
            Database::escape_string($db_name),
            Database::escape_string($course_language),
            Database::escape_string($title),
            Database::escape_string($description),
            Database::escape_string($category_code),
            Database::escape_string($tutor_name),
            Database::escape_string($visual_code),
            Database::escape_string($request_date),
            Database::escape_string($objectives),
            Database::escape_string($target_audience),
            Database::escape_string($status),
            Database::escape_string($info),
            Database::escape_string($exemplary_content)
        );

        $result_sql = Database::query($sql);

        if (!$result_sql) {
            return false;
        }

        $last_insert_id = Database::insert_id();

        // E-mail notifications.
        
        $email_language = $user_info['language'];
        $email_language_admin = api_get_setting('platformLanguage');

        $email_subject = sprintf(get_lang('CourseRequestEmailSubject', null, $email_language), '['.api_get_setting('siteName').']', $code);

        $email_body = get_lang('CourseRequestMailOpening', null, $email_language)."\n\n";
        $email_body .= get_lang('CourseName', null, $email_language).': '.$title."\n";
        $email_body .= get_lang('Fac', null, $email_language).': '.$category_code."\n";
        $email_body .= get_lang('CourseCode', null, $email_language).': '.$code."\n";
        $email_body .= get_lang('Professor', null, $email_language).': '.api_get_person_name($user_info['firstname'], $user_info['lastname'], null, null, $email_language)."\n";
        $email_body .= get_lang('Email', null, $email_language).': '.$user_info['mail']."\n";
        $email_body .= get_lang('Description', null, $email_language).': '.$description."\n";
        $email_body .= get_lang('Objectives', null, $email_language).': '.$objectives."\n";
        $email_body .= get_lang('TargetAudience', null, $email_language).': '.$target_audience."\n";
        $email_body .= get_lang('Ln', null, $email_language).': '.$course_language."\n";
        $email_body .= get_lang('FillWithExemplaryContent', null, $email_language).': '.($exemplary_content ? get_lang('Yes', null, $email_language) : get_lang('No', null, $email_language))."\n";
        $email_body = nl2br($email_body);
        
        // Sending an e-mail to the platform administrator.
        $email_body_admin = $email_body;
        $email_body_admin .= "\n".get_lang('CourseRequestPageForApproval', null, $email_language_admin).' '.api_get_path(WEB_CODE_PATH).'admin/course_request_edit.php?id='.$last_insert_id."\n";
        $email_body_admin .= "\n".get_lang('CourseRequestLegalNote', null, $email_language_admin)."\n";
        $email_body_admin = nl2br($email_body_admin);
        
        $sender_name_teacher = api_get_person_name($user_info['firstname'], $user_info['lastname'], null, PERSON_NAME_EMAIL_ADDRESS);
        $sender_email_teacher = $user_info['mail'];
        $recipient_name_admin = api_get_person_name(
            api_get_setting('administratorName'),
            api_get_setting('administratorSurname'),
            null,
            PERSON_NAME_EMAIL_ADDRESS
        );
        $recipient_email_admin = api_get_setting('emailAdministrator');

        $userInfo = api_get_user_info($user_id);

        $additionalParameters = [
            'smsType' => SmsPlugin::NEW_COURSE_SUGGESTED_TEACHER,
            'userId' => $user_id,
            'userUsername' => $userInfo['username'],
        ];

        api_mail_html(
            $recipient_name_admin,
            $recipient_email_admin,
            $email_subject,
            $email_body_admin,
            $sender_name_teacher,
            $sender_email_teacher,
            null,
            null,
            null,
            $additionalParameters
        );

        // Sending an e-mail to the requestor.

        $email_body_teacher = get_lang('Dear', null, $email_language).' ';
        $email_body_teacher .= api_get_person_name($user_info['firstname'], $user_info['lastname'], null, null, $email_language).",\n\n";
        $email_body_teacher .= $email_body;
        $email_body_teacher .= "\n".get_lang('SignatureFormula', null, $email_language)."\n";
        $email_body_teacher .= api_get_person_name(
                api_get_setting('administratorName'),
                api_get_setting('administratorSurname'),
                null,
                null,
                $email_language
            )."\n";
        $email_body_teacher .= get_lang('Manager', null, $email_language).' '.api_get_setting('siteName')."\n";
        $email_body_teacher .= get_lang('Phone', null, $email_language).': '.api_get_setting('administratorTelephone')."\n";
        $email_body_teacher .= get_lang('Email', null, $email_language).': '.api_get_setting('emailAdministrator', null, $email_language)."\n";
        $email_body_teacher .= "\n".get_lang('CourseRequestLegalNote', null, $email_language)."\n";
        $email_body_teacher = nl2br($email_body_teacher);
        
        // Swap the sender and the recipient.
        $sender_name_admin = $recipient_name_admin;
        $sender_email_admin = $recipient_email_admin;
        $recipient_name_teacher = $sender_name_teacher;
        $recipient_email_teacher = $sender_email_teacher;

        $additionalParameters = [
            'smsType' => SmsPlugin::COURSE_OPENING_REQUEST_CODE_REGISTERED,
            'userId' => $user_info['user_id'],
            'courseCode' => $wanted_code,
        ];

        api_mail_html(
            $recipient_name_teacher,
            $recipient_email_teacher,
            $email_subject,
            $email_body_teacher,
            $sender_name_admin,
            $sender_email_admin,
            null,
            null,
            null,
            $additionalParameters
        );

        return $last_insert_id;
    }

    /**
     * Updates a given course request in the database.
     *
     * @param int    $id              the id (an integer number) of the corresponding database record
     * @param string $wanted_code     the code for the created in the future course
     * @param string $title
     * @param string $description
     * @param string $category_code
     * @param string $course_language
     * @param string $objectives
     * @param string $target_audience
     * @param int    $user_id
     *
     * @return bool returns TRUE on success or FALSE on failure
     */
    public static function update_course_request(
        $id,
        $wanted_code,
        $title,
        $description,
        $category_code,
        $course_language,
        $objectives,
        $target_audience,
        $user_id,
        $exemplary_content
    ) {
        $id = (int) $id;
        $wanted_code = trim($wanted_code);
        $user_id = (int) $user_id;
        $exemplary_content = (bool) $exemplary_content ? 1 : 0;

        if ('' == $wanted_code) {
            return false;
        }

        if ($user_id <= 0) {
            return false;
        }

        // Retrieve request data
        $course_request_info = self::get_course_request_info($id);
        if (!is_array($course_request_info)) {
            return false;
        }

        $code = $wanted_code;
        $tutor_name = $course_request_info['tutor_name'];
        $directory = $course_request_info['directory'];
        $visual_code = $course_request_info['visual_code'];
        $request_date = $course_request_info['request_date'];
        $status = $course_request_info['status'];
        $info = $course_request_info['info'];

        if ($wanted_code != $course_request_info['code']) {
            if (self::course_code_exists($wanted_code)) {
                return false;
            }
            $keys = AddCourse::define_course_keys($wanted_code, '');
            if (count($keys)) {
                $visual_code = $keys['currentCourseCode'];
                $code = $keys['currentCourseId'];
                $db_name = $keys['currentCourseDbName'];
                $directory = $keys['currentCourseRepository'];
            } else {
                return false;
            }
        }

        if ($user_id != $course_request_info['code']) {
            $user_info = api_get_user_info($user_id);
            if (is_array($user_info)) {
                $tutor_name = api_get_person_name(
                    $user_info['firstname'],
                    $user_info['lastname'],
                    null,
                    null,
                    $course_language
                );
            } else {
                $user_id = $course_request_info['code'];
            }
        }

        if ($course_language != $course_request_info['course_language']) {
            $user_info = api_get_user_info($user_id);
            if (is_array($user_info)) {
                $tutor_name = api_get_person_name(
                    $user_info['firstname'],
                    $user_info['lastname'],
                    null,
                    null,
                    $course_language
                );
            }
        }

        // @todo use entity
        $sql = sprintf(
            'UPDATE %s SET
                code = "%s", user_id = "%s", directory = "%s", db_name = "%s",
                course_language = "%s", title = "%s", description = "%s", category_code = "%s",
                tutor_name = "%s", visual_code = "%s", request_date = "%s",
                objetives = "%s", target_audience = "%s", status = "%s", info = "%s", exemplary_content = "%s"
            WHERE id = '.$id,
            Database::get_main_table(TABLE_MAIN_COURSE_REQUEST),
            Database::escape_string($code),
            intval($user_id),
            Database::escape_string($directory),
            Database::escape_string($db_name),
            Database::escape_string($course_language),
            Database::escape_string($title),
            Database::escape_string($description),
            Database::escape_string($category_code),
            Database::escape_string($tutor_name),
            Database::escape_string($visual_code),
            Database::escape_string($request_date),
            Database::escape_string($objectives),
            Database::escape_string($target_audience),
            Database::escape_string($status),
            Database::escape_string($info),
            Database::escape_string($exemplary_content)
        );
        $result_sql = Database::query($sql);

        return false !== $result_sql;
    }

    /**
     * Deletes a given course request.
     *
     * @param int $id the id (an integer number) of the corresponding database record
     *
     * @return bool returns TRUE on success or FALSE on failure
     */
    public static function delete_course_request($id)
    {
        $id = (int) $id;
        $sql = "DELETE FROM ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)."
                WHERE id = ".$id;
        $result = Database::query($sql);

        return false !== $result;
    }

    /**
     * Returns the number of course requests in the course_request table (optionally matching a status).
     *
     * @param int $status
     *
     * @return bool
     */
    public static function count_course_requests($status = null)
    {
        $course_table = Database::get_main_table(TABLE_MAIN_COURSE_REQUEST);
        if (is_null($status)) {
            $sql = "SELECT COUNT(id) AS number FROM ".$course_table;
        } else {
            $status = (int) $status;
            $sql = "SELECT COUNT(id) AS number FROM ".$course_table."
                    WHERE status = ".$status;
        }
        $result = Database::fetch_array(Database::query($sql));
        if (is_array($result)) {
            return $result['number'];
        }

        return false;
    }

    /**
     * Gets all the information about a course request using its database id as an access key.
     *
     * @param int $id the id (an integer number) of the corresponding database record
     *
     * @return string|bool returns the requested data as an array or FALSE on failure
     */
    public static function get_course_request_info($id)
    {
        $id = (int) $id;
        $sql = "SELECT *
                FROM ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)."
                WHERE id = ".$id;
        $result = Database::query($sql);
        if (Database::num_rows($result) > 0) {
            return Database::fetch_array($result);

The expression return Database::fetch_array($result) also could return the type array which is incompatible with the documented return type boolean|string.

        }

        return false;
    }

    /**
     * Gets the code of a given course request using its database id as an access key.
     *
     * @param int $id the id (an integer number) of the corresponding database record
     *
     * @return string|bool returns the requested requested code or FALSE on failure
     */
    public static function get_course_request_code($id)
    {
        $id = (int) $id;
        $sql = "SELECT code
                FROM ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)."
                WHERE id = ".$id;
        $result = Database::query($sql);
        if (Database::num_rows($result) > 0) {
            $result_array = Database::fetch_array($result, 'NUM');
            if (is_array($result_array)) {
                return $result_array[0];
            }
        }

        return false;
    }

    /**
     * Accepts a given by its id course request. The requested course gets created immediately after the request acceptance.
     *
     * @param int $id the id (an integer number) of the corresponding database record
     *
     * @return string|bool returns the code of the newly created course or FALSE on failure
     */
    public static function accept_course_request($id)
    {
        $id = (int) $id;

        // Retrieve request's data
        $course_request_info = self::get_course_request_info($id);
        if (!is_array($course_request_info)) {
            return false;
        }

        // Make all the checks again before the new course creation.
        /*if (CourseManager::course_code_exists($wanted_code)) {
            return false;
        }*/

        $user_id = (int) $course_request_info['user_id'];
        if ($user_id <= 0) {
            return false;
        }

        $user_info = api_get_user_info($user_id);
        if (!is_array($user_info)) {
            return false;
        }

        // Create the requested course
        $params = [];

        $params['title'] = $course_request_info['title'];
        $params['course_category'] = $course_request_info['category_code'];
        $params['course_language'] = $course_request_info['course_language'];
        $params['exemplary_content'] = intval($course_request_info['exemplary_content']) > 0;
        $params['wanted_code'] = $course_request_info['code'];
        $params['user_id'] = $course_request_info['user_id'];
        $params['tutor_name'] = api_get_person_name($user_info['firstname'], $user_info['lastname']);

        $course_info = CourseManager::create_course($params);
        if (!empty($course_info)) {
            // Mark the request as accepted.
            $sql = "UPDATE ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)."
                    SET status = ".COURSE_REQUEST_ACCEPTED."
                    WHERE id = ".$id;
            Database::query($sql);

            // E-mail notification.

            // E-mail language: The user language seems to be the best choice
            $email_language = $user_info['language'];
            $email_subject = sprintf(get_lang('CourseRequestAcceptedEmailSubject', null, $email_language), '['.api_get_setting('siteName').']', $course_info['code']);

            $email_body = get_lang('Dear', null, $email_language).' ';
            $email_body .= api_get_person_name($user_info['firstname'], $user_info['lastname'], null, null, $email_language).",\n\n";
            $email_body .= sprintf(
                get_lang(
                    'CourseRequestAcceptedEmailText',
                    null,
                    $email_language
                ),
                $course_info['code'],
                $course_info['code'],
                api_get_path(WEB_COURSE_PATH).$course_info['directory'].'/'
            )."\n";
            $email_body .= "\n".get_lang('SignatureFormula', null, $email_language)."\n";
            $email_body .= api_get_person_name(api_get_setting('administratorName'), api_get_setting('administratorSurname'), null, null, $email_language)."\n";
            $email_body .= get_lang('Manager', null, $email_language).' '.api_get_setting('siteName')."\n";
            $email_body .= get_lang('Phone', null, $email_language).': '.api_get_setting('administratorTelephone')."\n";
            $email_body .= get_lang('Email', null, $email_language).': '.api_get_setting('emailAdministrator', null, $email_language)."\n";
            $email_body .= "\n".get_lang('CourseRequestLegalNote', null, $email_language)."\n";
            $email_body = nl2br($email_body);
            
            $sender_name = api_get_person_name(api_get_setting('administratorName'), api_get_setting('administratorSurname'), null, PERSON_NAME_EMAIL_ADDRESS);
            $sender_email = api_get_setting('emailAdministrator');
            $recipient_name = api_get_person_name($user_info['firstname'], $user_info['lastname'], null, PERSON_NAME_EMAIL_ADDRESS);
            $recipient_email = $user_info['mail'];

            $additionalParameters = [
                'smsType' => SmsPlugin::COURSE_OPENING_REQUEST_CODE_APPROVED,
                'userId' => $user_id,
                'courseCode' => $course_info['code'],
            ];

            api_mail_html(
                $recipient_name,
                $recipient_email,
                $email_subject,
                $email_body,
                $sender_name,
                $sender_email,
                null,
                null,
                null,
                $additionalParameters
            );

            return $course_info['code'];
        }

        return false;
    }

    /**
     * Rejects a given course request.
     *
     * @param int $id the id (an integer number) of the corresponding database record
     *
     * @return bool returns TRUE on success or FALSE on failure
     */
    public static function reject_course_request($id)
    {
        $id = (int) $id;
        // Retrieve request's data
        $course_request_info = self::get_course_request_info($id);
        if (!is_array($course_request_info)) {
            return false;
        }

        $user_id = intval($course_request_info['user_id']);
        if ($user_id <= 0) {
            return false;
        }

        $user_info = api_get_user_info($user_id);
        if (!is_array($user_info)) {
            return false;
        }

        $code = $course_request_info['code'];

        $sql = "UPDATE ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)."
                SET status = ".COURSE_REQUEST_REJECTED."
                WHERE id = ".$id;
        if (false === Database::query($sql)) {
            return false;
        }

        // E-mail notification.

        // E-mail language: The user language seems to be the best choice.
        $email_language = $user_info['language'];

        $email_subject = sprintf(get_lang('CourseRequestRejectedEmailSubject', null, $email_language), '['.api_get_setting('siteName').']', $code);

        $email_body = get_lang('Dear', null, $email_language).' ';
        $email_body .= api_get_person_name($user_info['firstname'], $user_info['lastname'], null, null, $email_language).",\n\n";
        $email_body .= sprintf(get_lang('CourseRequestRejectedEmailText', null, $email_language), $code)."\n";
        $email_body .= "\n".get_lang('SignatureFormula', null, $email_language)."\n";
        $email_body .= api_get_person_name(api_get_setting('administratorName'), api_get_setting('administratorSurname'), null, null, $email_language)."\n";
        $email_body .= get_lang('Manager', null, $email_language).' '.api_get_setting('siteName')."\n";
        $email_body .= get_lang('Phone', null, $email_language).': '.api_get_setting('administratorTelephone')."\n";
        $email_body .= get_lang('Email', null, $email_language).': '.api_get_setting('emailAdministrator', null, $email_language)."\n";
        $email_body .= "\n".get_lang('CourseRequestLegalNote', null, $email_language)."\n";
        $email_body = nl2br($email_body);
        
        $sender_name = api_get_person_name(
            api_get_setting('administratorName'),
            api_get_setting('administratorSurname'),
            null,
            PERSON_NAME_EMAIL_ADDRESS
        );
        $sender_email = api_get_setting('emailAdministrator');
        $recipient_name = api_get_person_name(
            $user_info['firstname'],
            $user_info['lastname'],
            null,
            PERSON_NAME_EMAIL_ADDRESS
        );
        $recipient_email = $user_info['mail'];

        $additionalParameters = [
            'smsType' => SmsPlugin::COURSE_OPENING_REQUEST_CODE_REJECTED,
            'userId' => $user_id,
            'courseCode' => $code,
        ];

        api_mail_html(
            $recipient_name,
            $recipient_email,
            $email_subject,
            $email_body,
            $sender_name,
            $sender_email,
            null,
            null,
            null,
            $additionalParameters
        );

        return true;
    }

    /**
     * Asks the author (through e-mail) for additional information about the given course request.
     *
     * @param int $id the database primary id of the given request
     *
     * @return bool returns TRUE on success or FALSE on failure
     */
    public static function ask_for_additional_info($id)
    {
        $id = (int) $id;

        // Retrieve request's data
        $course_request_info = self::get_course_request_info($id);
        if (!is_array($course_request_info)) {
            return false;
        }

        $user_id = intval($course_request_info['user_id']);
        if ($user_id <= 0) {
            return false;
        }

        $user_info = api_get_user_info($user_id);
        if (!is_array($user_info)) {
            return false;
        }

        $code = $course_request_info['code'];
        $info = intval($course_request_info['info']);

        // Error is to be returned on a repeated attempt for asking additional information.
        if (!empty($info)) {
            return false;
        }

        // E-mail notification.

        // E-mail language: The user language seems to be the best choice.
        $email_language = $user_info['language'];
        $email_subject = sprintf(get_lang('CourseRequestAskInfoEmailSubject', null, $email_language), '['.api_get_setting('siteName').']', $code);

        $email_body = get_lang('Dear', null, $email_language).' ';
        $email_body .= api_get_person_name($user_info['firstname'], $user_info['lastname'], null, null, $email_language).",\n\n";
        $email_body .= sprintf(get_lang('CourseRequestAskInfoEmailText', null, $email_language), $code)."\n";
        $email_body .= "\n".get_lang('SignatureFormula', null, $email_language)."\n";
        $email_body .= api_get_person_name(api_get_setting('administratorName'), api_get_setting('administratorSurname'))."\n";
        $email_body .= get_lang('Manager', null, $email_language).' '.api_get_setting('siteName')."\n";
        $email_body .= get_lang('Phone', null, $email_language).': '.api_get_setting('administratorTelephone')."\n";
        $email_body .= get_lang('Email', null, $email_language).': '.api_get_setting('emailAdministrator')."\n";
        $email_body .= "\n".get_lang('CourseRequestLegalNote', null, $email_language)."\n";
        $email_body = nl2br($email_body);
        
        $sender_name = api_get_person_name(
            api_get_setting('administratorName'),
            api_get_setting('administratorSurname'),
            null,
            PERSON_NAME_EMAIL_ADDRESS
        );
        $sender_email = api_get_setting('emailAdministrator');
        $recipient_name = api_get_person_name(
            $user_info['firstname'],
            $user_info['lastname'],
            null,
            PERSON_NAME_EMAIL_ADDRESS
        );
        $recipient_email = $user_info['mail'];

        $additionalParameters = [
            'smsType' => SmsPlugin::COURSE_OPENING_REQUEST_CODE,
            'userId' => $user_id,
            'courseCode' => $code,
        ];

        $result = api_mail_html(
            $recipient_name,
            $recipient_email,
            $email_subject,
            $email_body,
            $sender_name,
            $sender_email,
            null,
            null,
            null,
            $additionalParameters
        );

        if (!$result) {
            return false;
        }

        // Marking the fact that additional information about the request has been asked.
        $sql = "UPDATE ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)."
                SET info = 1 WHERE id = ".$id;
        $result = false !== Database::query($sql);

        return $result;
    }

    /**
     * Checks whether additional information about the given course request has been asked.
     *
     * @param int $id the database primary id of the given request
     *
     * @return bool returns TRUE if additional information has been asked or FALSE otherwise
     */
    public static function additional_info_asked($id)
    {
        $id = (int) $id;
        $sql = "SELECT id FROM ".Database::get_main_table(TABLE_MAIN_COURSE_REQUEST)."
                WHERE (id = ".$id." AND info > 0)";
        $result = Database::num_rows(Database::query($sql));

        return !empty($result);
    }
}