Kitodo\Dlf\Common\Document

Complexity

Total Complexity

274

Size/Duplication

Total Lines	1951
Duplicated Lines	0 %

Importance

Changes

0

44 Methods

Rating	Name	Duplication	Size	Complexity
A	getFileLocation()	0	7	3
F	getLogicalStructureInfo()	0	74	21
B	getLogicalStructure()	0	26	7
C	getInstance()	0	47	15
A	clearRegistry()	0	3	1
A	getFileMimeType()	0	7	3
A	_getLocation()	0	2	1
B	_getMetadataArray()	0	20	7
A	_getCPid()	0	2	1
A	_getToplevelId()	0	21	6
A	_getPhysicalStructureInfo()	0	7	2
A	__get()	0	8	3
B	_getDmdSec()	0	27	8
A	init()	0	10	2
A	_getPid()	0	2	1
A	getPhysicalPage()	0	16	5
B	getTitle()	0	31	7
A	_getParentId()	0	2	1
A	__clone()	0	1	1
A	_getReady()	0	2	1
A	getTitledata()	0	11	5
B	_getThumbnail()	0	56	11
A	_getRootId()	0	9	3
A	_getRecordId()	0	2	1
A	_getUid()	0	2	1
B	getRawText()	0	52	8
A	registerNamespaces()	0	14	4
A	load()	0	30	4
C	__construct()	0	81	17
B	_getFileGrps()	0	35	11
A	__sleep()	0	4	1
F	save()	0	273	37
A	_getHasFulltext()	0	6	2
A	_getTableOfContents()	0	8	2
A	_getSmLinks()	0	10	3
C	_getPhysicalStructure()	0	52	17
A	__toString()	0	5	1
A	__set()	0	7	3
A	loadFormats()	0	21	3
A	_getNumPages()	0	3	1
F	getMetadata()	0	164	39
A	_setCPid()	0	2	1
A	__wakeup()	0	14	2
A	_getMets()	0	2	1

<?php
namespace Kitodo\Dlf\Common;

/**
 * (c) Kitodo. Key to digital objects e.V. <contact@kitodo.org>
 *
 * This file is part of the Kitodo and TYPO3 projects.
 *
 * @license GNU General Public License version 3 or later.
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 */

/**
 * Document class for the 'dlf' extension
 *
 * @author Sebastian Meyer <sebastian.meyer@slub-dresden.de>
 * @author Henrik Lochmann <dev@mentalmotive.com>
 * @package TYPO3
 * @subpackage dlf
 * @access public
 */
final class Document {
    /**
     * This holds the whole XML file as string for serialization purposes
     * @see __sleep() / __wakeup()
     *
     * @var string
     * @access protected
     */
    protected $asXML = '';

    /**
     * This holds the PID for the configuration
     *
     * @var integer
     * @access protected
     */
    protected $cPid = 0;

    /**
     * This holds the XML file's dmdSec parts with their IDs as array key
     *
     * @var array
     * @access protected
     */
    protected $dmdSec = [];

    /**
     * Are the METS file's dmdSecs loaded?
     * @see $dmdSec
     *
     * @var boolean
     * @access protected
     */
    protected $dmdSecLoaded = FALSE;

    /**
     * The extension key
     *
     * @var string
     * @access public
     */
    public static $extKey = 'dlf';

    /**
     * This holds the file ID -> USE concordance
     * @see _getFileGrps()
     *
     * @var array
     * @access protected
     */
    protected $fileGrps = [];

    /**
     * Are the file groups loaded?
     * @see $fileGrps
     *
     * @var boolean
     * @access protected
     */
    protected $fileGrpsLoaded = FALSE;

    /**
     * This holds the configuration for all supported metadata encodings
     * @see loadFormats()
     *
     * @var array
     * @access protected
     */
    protected $formats = [
        'OAI' => [
            'rootElement' => 'OAI-PMH',
            'namespaceURI' => 'http://www.openarchives.org/OAI/2.0/',
        ],
        'METS' => [
            'rootElement' => 'mets',
            'namespaceURI' => 'http://www.loc.gov/METS/',
        ],
        'XLINK' => [
            'rootElement' => 'xlink',
            'namespaceURI' => 'http://www.w3.org/1999/xlink',
        ]
    ];

    /**
     * Are the available metadata formats loaded?
     * @see $formats
     *
     * @var boolean
     * @access protected
     */
    protected $formatsLoaded = FALSE;

    /**
     * Are there any fulltext files available?
     *
     * @var boolean
     * @access protected
     */
    protected $hasFulltext = FALSE;

    /**
     * Last searched logical and physical page
     *
     * @var array
     * @access protected
     */
    protected $lastSearchedPhysicalPage = ['logicalPage' => NULL, 'physicalPage' => NULL];

    /**
     * This holds the documents location
     *
     * @var string
     * @access protected
     */
    protected $location = '';

    /**
     * This holds the logical units
     *
     * @var array
     * @access protected
     */
    protected $logicalUnits = [];

    /**
     * This holds the documents' parsed metadata array with their corresponding structMap//div's ID as array key
     *
     * @var array
     * @access protected
     */
    protected $metadataArray = [];

    /**
     * Is the metadata array loaded?
     * @see $metadataArray
     *
     * @var boolean
     * @access protected
     */
    protected $metadataArrayLoaded = FALSE;

    /**
     * This holds the XML file's METS part as \SimpleXMLElement object
     *
     * @var \SimpleXMLElement
     * @access protected
     */
    protected $mets;

    /**
     * The holds the total number of pages
     *
     * @var integer
     * @access protected
     */
    protected $numPages = 0;

    /**
     * This holds the UID of the parent document or zero if not multi-volumed
     *
     * @var integer
     * @access protected
     */
    protected $parentId = 0;

    /**
     * This holds the physical structure
     *
     * @var array
     * @access protected
     */
    protected $physicalStructure = [];

    /**
     * This holds the physical structure metadata
     *
     * @var array
     * @access protected
     */
    protected $physicalStructureInfo = [];

    /**
     * Is the physical structure loaded?
     * @see $physicalStructure
     *
     * @var boolean
     * @access protected
     */
    protected $physicalStructureLoaded = FALSE;

    /**
     * This holds the PID of the document or zero if not in database
     *
     * @var integer
     * @access protected
     */
    protected $pid = 0;

    /**
     * This holds the documents' raw text pages with their corresponding structMap//div's ID as array key
     *
     * @var array
     * @access protected
     */
    protected $rawTextArray = [];

    /**
     * Is the document instantiated successfully?
     *
     * @var boolean
     * @access protected
     */
    protected $ready = FALSE;

    /**
     * The METS file's record identifier
     *
     * @var string
     * @access protected
     */
    protected $recordId;

    /**
     * This holds the singleton object of the document
     *
     * @var array (\Kitodo\Dlf\Common\Document)
     * @access protected
     */
    protected static $registry = [];

    /**
     * This holds the UID of the root document or zero if not multi-volumed
     *
     * @var integer
     * @access protected
     */
    protected $rootId = 0;

    /**
     * Is the root id loaded?
     * @see $rootId
     *
     * @var boolean
     * @access protected
     */
    protected $rootIdLoaded = FALSE;

    /**
     * This holds the smLinks between logical and physical structMap
     *
     * @var array
     * @access protected
     */
    protected $smLinks = ['l2p' => [], 'p2l' => []];

    /**
     * Are the smLinks loaded?
     * @see $smLinks
     *
     * @var boolean
     * @access protected
     */
    protected $smLinksLoaded = FALSE;

    /**
     * This holds the logical structure
     *
     * @var array
     * @access protected
     */
    protected $tableOfContents = [];

    /**
     * Is the table of contents loaded?
     * @see $tableOfContents
     *
     * @var boolean
     * @access protected
     */
    protected $tableOfContentsLoaded = FALSE;

    /**
     * This holds the document's thumbnail location.
     *
     * @var string
     * @access protected
     */
    protected $thumbnail = '';

    /**
     * Is the document's thumbnail location loaded?
     * @see $thumbnail
     *
     * @var boolean
     * @access protected
     */
    protected $thumbnailLoaded = FALSE;

    /**
     * This holds the toplevel structure's @ID
     *
     * @var string
     * @access protected
     */
    protected $toplevelId = '';

    /**
     * This holds the UID or the URL of the document
     *
     * @var mixed
     * @access protected
     */
    protected $uid = 0;

    /**
     * This holds the whole XML file as \SimpleXMLElement object
     *
     * @var \SimpleXMLElement
     * @access protected
     */
    protected $xml;

    /**
     * This clears the static registry to prevent memory exhaustion
     *
     * @access public
     *
     * @return void
     */
    public static function clearRegistry() {
        // Reset registry array.
        self::$registry = [];
    }

    /**
     * This gets the location of a file representing a physical page or track
     *
     * @access public
     *
     * @param string $id: The @ID attribute of the file node
     *
     * @return string The file's location as URL
     */
    public function getFileLocation($id) {
        if (!empty($id)
            && ($location = $this->mets->xpath('./mets:fileSec/mets:fileGrp/mets:file[@ID="'.$id.'"]/mets:FLocat[@LOCTYPE="URL"]'))) {
            return (string) $location[0]->attributes('http://www.w3.org/1999/xlink')->href;
        } else {
            Helper::devLog('There is no file node with @ID "'.$id.'"', DEVLOG_SEVERITY_WARNING);
            return '';
        }
    }

    /**
     * This gets the MIME type of a file representing a physical page or track
     *
     * @access public
     *
     * @param string $id: The @ID attribute of the file node
     *
     * @return string The file's MIME type
     */
    public function getFileMimeType($id) {
        if (!empty($id)
            && ($mimetype = $this->mets->xpath('./mets:fileSec/mets:fileGrp/mets:file[@ID="'.$id.'"]/@MIMETYPE'))) {
            return (string) $mimetype[0];
        } else {
            Helper::devLog('There is no file node with @ID "'.$id.'" or no MIME type specified', DEVLOG_SEVERITY_WARNING);
            return '';
        }
    }

    /**
     * This is a singleton class, thus an instance must be created by this method
     *
     * @access public
     *
     * @param mixed $uid: The unique identifier of the document to parse or URL of XML file
     * @param integer $pid: If > 0, then only document with this PID gets loaded
     * @param boolean $forceReload: Force reloading the document instead of returning the cached instance
     *
     * @return \Kitodo\Dlf\Common\Document Instance of this class
     */
    public static function &getInstance($uid, $pid = 0, $forceReload = FALSE) {
        // Sanitize input.
        $pid = max(intval($pid), 0);
        if (!$forceReload) {
            $regObj = md5($uid);
            if (is_object(self::$registry[$regObj])
                && self::$registry[$regObj] instanceof self) {
                // Check if instance has given PID.
                if (!$pid
                    || !self::$registry[$regObj]->pid
                    || $pid == self::$registry[$regObj]->pid) {
                    // Return singleton instance if available.
                    return self::$registry[$regObj];
                }
            } else {
                // Check the user's session...
                $sessionData = Helper::loadFromSession(get_called_class());
                if (is_object($sessionData[$regObj])
                    && $sessionData[$regObj] instanceof self) {
                    // Check if instance has given PID.
                    if (!$pid
                        || !$sessionData[$regObj]->pid
                        || $pid == $sessionData[$regObj]->pid) {
                        // ...and restore registry.
                        self::$registry[$regObj] = $sessionData[$regObj];
                        return self::$registry[$regObj];
                    }
                }
            }
        }
        // Create new instance...
        $instance = new self($uid, $pid);
        // ...and save it to registry.
        if ($instance->ready) {
            self::$registry[md5($instance->uid)] = $instance;
            if ($instance->uid != $instance->location) {
                self::$registry[md5($instance->location)] = $instance;
            }
            // Load extension configuration
            $extConf = unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf']['dlf']);
            // Save registry to session if caching is enabled.
            if (!empty($extConf['caching'])) {
                Helper::saveToSession(self::$registry, get_class($instance));
            }
        }
        // Return new instance.
        return $instance;
    }

    /**
     * This gets details about a logical structure element
     *
     * @access public
     *
     * @param string $id: The @ID attribute of the logical structure node
     * @param boolean $recursive: Whether to include the child elements
     *
     * @return array Array of the element's id, label, type and physical page indexes/mptr link
     */
    public function getLogicalStructure($id, $recursive = FALSE) {
        $details = [];
        // Is the requested logical unit already loaded?
        if (!$recursive
            && !empty($this->logicalUnits[$id])) {
            // Yes. Return it.
            return $this->logicalUnits[$id];
        } elseif (!empty($id)) {
            // Get specified logical unit.
            $divs = $this->mets->xpath('./mets:structMap[@TYPE="LOGICAL"]//mets:div[@ID="'.$id.'"]');
        } else {
            // Get all logical units at top level.
            $divs = $this->mets->xpath('./mets:structMap[@TYPE="LOGICAL"]/mets:div');
        }
        if (!empty($divs)) {
            if (!$recursive) {
                // Get the details for the first xpath hit.
                $details = $this->getLogicalStructureInfo($divs[0]);
            } else {
                // Walk the logical structure recursively and fill the whole table of contents.
                foreach ($divs as $div) {
                    $this->tableOfContents[] = $this->getLogicalStructureInfo($div, TRUE);
                }
            }
        }
        return $details;
    }

    /**
     * This gets details about a logical structure element
     *
     * @access protected
     *
     * @param \SimpleXMLElement $structure: The logical structure node
     * @param boolean $recursive: Whether to include the child elements
     *
     * @return array Array of the element's id, label, type and physical page indexes/mptr link
     */
    protected function getLogicalStructureInfo(\SimpleXMLElement $structure, $recursive = FALSE) {
        // Get attributes.
        foreach ($structure->attributes() as $attribute => $value) {
            $attributes[$attribute] = (string) $value;
        }
        // Load plugin configuration.
        $extConf = unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf'][self::$extKey]);
        // Extract identity information.
        $details = [];
        $details['id'] = $attributes['ID'];

The variable $attributes seems to be defined by a foreach iteration on line 505. Are you sure the iterator is never empty, otherwise this variable is not defined?

        $details['dmdId'] = (isset($attributes['DMDID']) ? $attributes['DMDID'] : '');
        $details['label'] = (isset($attributes['LABEL']) ? $attributes['LABEL'] : '');
        $details['orderlabel'] = (isset($attributes['ORDERLABEL']) ? $attributes['ORDERLABEL'] : '');
        $details['contentIds'] = (isset($attributes['CONTENTIDS']) ? $attributes['CONTENTIDS'] : '');
        $details['volume'] = '';
        // Set volume information only if no label is set and this is the toplevel structure element.
        if (empty($details['label'])
            && $details['id'] == $this->_getToplevelId()) {
            $metadata = $this->getMetadata($details['id']);
            if (!empty($metadata['volume'][0])) {
                $details['volume'] = $metadata['volume'][0];
            }
        }
        $details['pagination'] = '';
        $details['type'] = $attributes['TYPE'];
        $details['thumbnailId'] = '';
        // Load smLinks.
        $this->_getSmLinks();
        // Load physical structure.
        $this->_getPhysicalStructure();
        // Get the physical page or external file this structure element is pointing at.
        $details['points'] = '';
        // Is there a mptr node?
        if (count($structure->children('http://www.loc.gov/METS/')->mptr)) {
            // Yes. Get the file reference.
            $details['points'] = (string) $structure->children('http://www.loc.gov/METS/')->mptr[0]->attributes('http://www.w3.org/1999/xlink')->href;
        } elseif (!empty($this->physicalStructure)
            && array_key_exists($details['id'], $this->smLinks['l2p'])) { // Are there any physical elements and is this logical unit linked to at least one of them?
            $details['points'] = max(intval(array_search($this->smLinks['l2p'][$details['id']][0], $this->physicalStructure, TRUE)), 1);
            if (!empty($this->physicalStructureInfo[$this->smLinks['l2p'][$details['id']][0]]['files'][$extConf['fileGrpThumbs']])) {
                $details['thumbnailId'] = $this->physicalStructureInfo[$this->smLinks['l2p'][$details['id']][0]]['files'][$extConf['fileGrpThumbs']];
            }
            // Get page/track number of the first page/track related to this structure element.
            $details['pagination'] = $this->physicalStructureInfo[$this->smLinks['l2p'][$details['id']][0]]['orderlabel'];
        } elseif ($details['id'] == $this->_getToplevelId()) { // Is this the toplevel structure element?
            // Yes. Point to itself.
            $details['points'] = 1;
            if (!empty($this->physicalStructure)
                && !empty($this->physicalStructureInfo[$this->physicalStructure[1]]['files'][$extConf['fileGrpThumbs']])) {
                $details['thumbnailId'] = $this->physicalStructureInfo[$this->physicalStructure[1]]['files'][$extConf['fileGrpThumbs']];
            }
        }
        // Get the files this structure element is pointing at.
        $details['files'] = [];
        $fileUse = $this->_getFileGrps();
        // Get the file representations from fileSec node.
        foreach ($structure->children('http://www.loc.gov/METS/')->fptr as $fptr) {
            // Check if file has valid @USE attribute.
            if (!empty($fileUse[(string) $fptr->attributes()->FILEID])) {
                $details['files'][$fileUse[(string) $fptr->attributes()->FILEID]] = (string) $fptr->attributes()->FILEID;
            }
        }
        // Keep for later usage.
        $this->logicalUnits[$details['id']] = $details;
        // Walk the structure recursively? And are there any children of the current element?
        if ($recursive
            && count($structure->children('http://www.loc.gov/METS/')->div)) {
            $details['children'] = [];
            foreach ($structure->children('http://www.loc.gov/METS/')->div as $child) {
                // Repeat for all children.
                $details['children'][] = $this->getLogicalStructureInfo($child, TRUE);
            }
        }
        return $details;
    }

    /**
     * This extracts all the metadata for a logical structure node
     *
     * @access public
     *
     * @param string $id: The @ID attribute of the logical structure node
     * @param integer $cPid: The PID for the metadata definitions
     *                       (defaults to $this->cPid or $this->pid)
     *
     * @return array The logical structure node's parsed metadata array
     */
    public function getMetadata($id, $cPid = 0) {
        // Make sure $cPid is a non-negative integer.
        $cPid = max(intval($cPid), 0);
        // If $cPid is not given, try to get it elsewhere.
        if (!$cPid
            && ($this->cPid || $this->pid)) {
            // Retain current PID.
            $cPid = ($this->cPid ? $this->cPid : $this->pid);
        } elseif (!$cPid) {
            Helper::devLog('Invalid PID '.$cPid.' for metadata definitions', DEVLOG_SEVERITY_WARNING);
            return [];
        }
        // Get metadata from parsed metadata array if available.
        if (!empty($this->metadataArray[$id])
            && $this->metadataArray[0] == $cPid) {
            return $this->metadataArray[$id];
        }
        // Initialize metadata array with empty values.
        $metadata = [
            'title' => [],
            'title_sorting' => [],
            'author' => [],
            'place' => [],
            'year' => [],
            'prod_id' => [],
            'record_id' => [],
            'opac_id' => [],
            'union_id' => [],
            'urn' => [],
            'purl' => [],
            'type' => [],
            'volume' => [],
            'volume_sorting' => [],
            'collection' => [],
            'owner' => [],
        ];
        // Get the logical structure node's DMDID.
        if (!empty($this->logicalUnits[$id])) {
            $dmdId = $this->logicalUnits[$id]['dmdId'];
        } else {
            $dmdId = $this->mets->xpath('./mets:structMap[@TYPE="LOGICAL"]//mets:div[@ID="'.$id.'"]/@DMDID');
            $dmdId = (string) $dmdId[0];
        }
        if (!empty($dmdId)) {
            // Load available metadata formats and dmdSecs.
            $this->loadFormats();
            $this->_getDmdSec();
            // Is this metadata format supported?
            if (!empty($this->formats[$this->dmdSec[$dmdId]['type']])) {
                if (!empty($this->formats[$this->dmdSec[$dmdId]['type']]['class'])) {
                    $class = $this->formats[$this->dmdSec[$dmdId]['type']]['class'];
                    // Get the metadata from class.
                    if (class_exists($class)
                        && ($obj = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance($class)) instanceof MetadataInterface) {
                        $obj->extractMetadata($this->dmdSec[$dmdId]['xml'], $metadata);
                    } else {
                        Helper::devLog('Invalid class/method "'.$class.'->extractMetadata()" for metadata format "'.$this->dmdSec[$dmdId]['type'].'"', DEVLOG_SEVERITY_WARNING);
                    }
                }
            } else {
                Helper::devLog('Unsupported metadata format "'.$this->dmdSec[$dmdId]['type'].'" in dmdSec with @ID "'.$dmdId.'"', DEVLOG_SEVERITY_WARNING);
                return [];
            }
            // Get the structure's type.
            if (!empty($this->logicalUnits[$id])) {
                $metadata['type'] = [$this->logicalUnits[$id]['type']];
            } else {
                $struct = $this->mets->xpath('./mets:structMap[@TYPE="LOGICAL"]//mets:div[@ID="'.$id.'"]/@TYPE');
                $metadata['type'] = [(string) $struct[0]];
            }
            // Get the additional metadata from database.
            $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
                'tx_dlf_metadata.index_name AS index_name,tx_dlf_metadataformat.xpath AS xpath,tx_dlf_metadataformat.xpath_sorting AS xpath_sorting,tx_dlf_metadata.is_sortable AS is_sortable,tx_dlf_metadata.default_value AS default_value,tx_dlf_metadata.format AS format',
                'tx_dlf_metadata,tx_dlf_metadataformat,tx_dlf_formats',
                'tx_dlf_metadata.pid='.$cPid
                    .' AND tx_dlf_metadataformat.pid='.$cPid
                    .' AND ((tx_dlf_metadata.uid=tx_dlf_metadataformat.parent_id AND tx_dlf_metadataformat.encoded=tx_dlf_formats.uid AND tx_dlf_formats.type='.$GLOBALS['TYPO3_DB']->fullQuoteStr($this->dmdSec[$dmdId]['type'], 'tx_dlf_formats').') OR tx_dlf_metadata.format=0)'
                    .Helper::whereClause('tx_dlf_metadata', TRUE)
                    .Helper::whereClause('tx_dlf_metadataformat')
                    .Helper::whereClause('tx_dlf_formats'),
                '',
                '',
                ''
            );
            // We need a \DOMDocument here, because SimpleXML doesn't support XPath functions properly.
            $domNode = dom_import_simplexml($this->dmdSec[$dmdId]['xml']);
            $domXPath = new \DOMXPath($domNode->ownerDocument);
            $this->registerNamespaces($domXPath);
            // OK, now make the XPath queries.
            while ($resArray = $GLOBALS['TYPO3_DB']->sql_fetch_assoc($result)) {
                // Set metadata field's value(s).
                if ($resArray['format'] > 0
                    && !empty($resArray['xpath'])
                    && ($values = $domXPath->evaluate($resArray['xpath'], $domNode))) {
                    if ($values instanceof \DOMNodeList
                        && $values->length > 0) {
                        $metadata[$resArray['index_name']] = [];
                        foreach ($values as $value) {
                            $metadata[$resArray['index_name']][] = trim((string) $value->nodeValue);
                        }
                    } elseif (!($values instanceof \DOMNodeList)) {
                        $metadata[$resArray['index_name']] = [trim((string) $values)];
                    }
                }
                // Set default value if applicable.
                // '!empty($resArray['default_value'])' is not possible, because '0' is a valid default value.
                // Setting an empty default value creates a lot of empty fields within the index.
                // These empty fields are then shown within the search facets as 'empty'.
                if (empty($metadata[$resArray['index_name']][0])
                    && strlen($resArray['default_value']) > 0) {
                    $metadata[$resArray['index_name']] = [$resArray['default_value']];
                }
                // Set sorting value if applicable.
                if (!empty($metadata[$resArray['index_name']])
                    && $resArray['is_sortable']) {
                    if ($resArray['format'] > 0
                        && !empty($resArray['xpath_sorting'])
                        && ($values = $domXPath->evaluate($resArray['xpath_sorting'], $domNode))) {
                        if ($values instanceof \DOMNodeList
                            && $values->length > 0) {
                            $metadata[$resArray['index_name'].'_sorting'][0] = trim((string) $values->item(0)->nodeValue);
                        } elseif (!($values instanceof \DOMNodeList)) {
                            $metadata[$resArray['index_name'].'_sorting'][0] = trim((string) $values);
                        }
                    }
                    if (empty($metadata[$resArray['index_name'].'_sorting'][0])) {
                        $metadata[$resArray['index_name'].'_sorting'][0] = $metadata[$resArray['index_name']][0];
                    }
                }
            }
            // Set title to empty string if not present.
            if (empty($metadata['title'][0])) {
                $metadata['title'][0] = '';
                $metadata['title_sorting'][0] = '';
            }
            // Add collections from database to toplevel element if document is already saved.
            if (\TYPO3\CMS\Core\Utility\MathUtility::canBeInterpretedAsInteger($this->uid)
                && $id == $this->_getToplevelId()) {
                $result = $GLOBALS['TYPO3_DB']->exec_SELECT_mm_query(
                    'tx_dlf_collections.index_name AS index_name',
                    'tx_dlf_documents',
                    'tx_dlf_relations',
                    'tx_dlf_collections',
                    'AND tx_dlf_collections.pid='.intval($cPid)
                        .' AND tx_dlf_documents.uid='.intval($this->uid)
                        .' AND tx_dlf_relations.ident='.$GLOBALS['TYPO3_DB']->fullQuoteStr('docs_colls', 'tx_dlf_relations')
                        .' AND tx_dlf_collections.sys_language_uid IN (-1,0)'
                        .Helper::whereClause('tx_dlf_documents')
                        .Helper::whereClause('tx_dlf_collections'),
                    'tx_dlf_collections.index_name',
                    '',
                    ''
                );
                while ($resArray = $GLOBALS['TYPO3_DB']->sql_fetch_assoc($result)) {
                    if (!in_array($resArray['index_name'], $metadata['collection'])) {
                        $metadata['collection'][] = $resArray['index_name'];
                    }
                }
            }
        } else {
            // There is no dmdSec for this structure node.
            return [];
        }
        return $metadata;
    }

    /**
     * This returns the first corresponding physical page number of a given logical page label
     *
     * @access public
     *
     * @param string $logicalPage: The label (or a part of the label) of the logical page
     *
     * @return integer The physical page number
     */
    public function getPhysicalPage($logicalPage) {
        if (!empty($this->lastSearchedPhysicalPage['logicalPage'])
            && $this->lastSearchedPhysicalPage['logicalPage'] == $logicalPage) {
            return $this->lastSearchedPhysicalPage['physicalPage'];
        } else {
            $physicalPage = 0;
            foreach ($this->physicalStructureInfo as $page) {
                if (strpos($page['orderlabel'], $logicalPage) !== FALSE) {
                    $this->lastSearchedPhysicalPage['logicalPage'] = $logicalPage;
                    $this->lastSearchedPhysicalPage['physicalPage'] = $physicalPage;
                    return $physicalPage;
                }
                $physicalPage++;
            }
        }
        return 1;
    }

    /**
     * This extracts the raw text for a physical structure node
     *
     * @access public
     *
     * @param string $id: The @ID attribute of the physical structure node
     *
     * @return string The physical structure node's raw text
     */
    public function getRawText($id) {
        $rawText = '';
        // Get text from raw text array if available.
        if (!empty($this->rawTextArray[$id])) {
            return $this->rawTextArray[$id];
        }
        // Load fileGrps and check for fulltext files.
        $this->_getFileGrps();
        if ($this->hasFulltext) {
            // Load available text formats, ...
            $this->loadFormats();
            // ... physical structure ...
            $this->_getPhysicalStructure();
            // ... and extension configuration.
            $extConf = unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf'][self::$extKey]);
            if (!empty($this->physicalStructureInfo[$id])) {
                // Get fulltext file.
                $file = $this->getFileLocation($this->physicalStructureInfo[$id]['files'][$extConf['fileGrpFulltext']]);
                // Turn off libxml's error logging.
                $libxmlErrors = libxml_use_internal_errors(TRUE);
                // Disables the functionality to allow external entities to be loaded when parsing the XML, must be kept.
                $previousValueOfEntityLoader = libxml_disable_entity_loader(TRUE);
                // Load XML from file.
                $rawTextXml = simplexml_load_string(\TYPO3\CMS\Core\Utility\GeneralUtility::getUrl($file));

It seems like TYPO3\CMS\Core\Utility\GeneralUtility::getUrl($file) can also be of type false; however, parameter $data of simplexml_load_string() does only seem to accept string, maybe add an additional type check?

                // Reset entity loader setting.
                libxml_disable_entity_loader($previousValueOfEntityLoader);
                // Reset libxml's error logging.
                libxml_use_internal_errors($libxmlErrors);
                // Get the root element's name as text format.
                $textFormat = strtoupper($rawTextXml->getName());
            } else {
                Helper::devLog('Invalid structure node @ID "'.$id.'"', DEVLOG_SEVERITY_WARNING);
                return $rawText;
            }
            // Is this text format supported?
            if (!empty($this->formats[$textFormat])) {
                if (!empty($this->formats[$textFormat]['class'])) {
                    $class = $this->formats[$textFormat]['class'];
                    // Get the raw text from class.
                    if (class_exists($class)
                        && ($obj = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance($class)) instanceof FulltextInterface) {
                        $rawText = $obj->getRawText($rawTextXml);

It seems like $rawTextXml can also be of type false; however, parameter $xml of Kitodo\Dlf\Common\FulltextInterface::getRawText() does only seem to accept SimpleXMLElement, maybe add an additional type check?

                        $this->rawTextArray[$id] = $rawText;
                    } else {
                        Helper::devLog('Invalid class/method "'.$class.'->getRawText()" for text format "'.$textFormat.'"', DEVLOG_SEVERITY_WARNING);
                    }
                }
            } else {
                Helper::devLog('Unsupported text format "'.$textFormat.'" in physical node with @ID "'.$id.'"', DEVLOG_SEVERITY_WARNING);
            }
        }
        return $rawText;
    }

    /**
     * This determines a title for the given document
     *
     * @access public
     *
     * @param integer $uid: The UID of the document
     * @param boolean $recursive: Search superior documents for a title, too?
     *
     * @return string The title of the document itself or a parent document
     */
    public static function getTitle($uid, $recursive = FALSE) {
        $title = '';
        // Sanitize input.
        $uid = max(intval($uid), 0);
        if ($uid) {
            $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
                'tx_dlf_documents.title,tx_dlf_documents.partof',
                'tx_dlf_documents',
                'tx_dlf_documents.uid='.$uid
                    .Helper::whereClause('tx_dlf_documents'),
                '',
                '',
                '1'
            );
            if ($GLOBALS['TYPO3_DB']->sql_num_rows($result)) {
                // Get title information.
                list ($title, $partof) = $GLOBALS['TYPO3_DB']->sql_fetch_row($result);
                // Search parent documents recursively for a title?
                if ($recursive
                    && empty($title)
                    && intval($partof)
                    && $partof != $uid) {
                    $title = self::getTitle($partof, TRUE);
                }
            } else {
                Helper::devLog('No document with UID '.$uid.' found or document not accessible', DEVLOG_SEVERITY_WARNING);
            }
        } else {
            Helper::devLog('Invalid UID '.$uid.' for document', DEVLOG_SEVERITY_ERROR);
        }
        return $title;
    }

    /**
     * This extracts all the metadata for the toplevel logical structure node
     *
     * @access public
     *
     * @param integer $cPid: The PID for the metadata definitions
     *
     * @return array The logical structure node's parsed metadata array
     */
    public function getTitledata($cPid = 0) {
        $titledata = $this->getMetadata($this->_getToplevelId(), $cPid);
        // Set record identifier for METS file if not present.
        if (is_array($titledata)
            && array_key_exists('record_id', $titledata)) {
            if (!empty($this->recordId)
                && !in_array($this->recordId, $titledata['record_id'])) {
                array_unshift($titledata['record_id'], $this->recordId);
            }
        }
        return $titledata;
    }

    /**
     * This sets some basic class properties
     *
     * @access protected
     *
     * @return void
     */
    protected function init() {
        // Get METS node from XML file.
        $this->registerNamespaces($this->xml);
        $mets = $this->xml->xpath('//mets:mets');
        if ($mets) {
            $this->mets = $mets[0];
            // Register namespaces.
            $this->registerNamespaces($this->mets);
        } else {
            Helper::devLog('No METS part found in document with UID '.$this->uid, DEVLOG_SEVERITY_ERROR);
        }
    }

    /**
     * Load XML file from URL
     *
     * @access protected
     *
     * @param string $location: The URL of the file to load
     *
     * @return boolean TRUE on success or FALSE on failure
     */
    protected function load($location) {
        // Load XML file.
        if (\TYPO3\CMS\Core\Utility\GeneralUtility::isValidUrl($location)) {
            // Load extension configuration
            $extConf = unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf']['dlf']);
            // Set user-agent to identify self when fetching XML data.
            if (!empty($extConf['useragent'])) {
                @ini_set('user_agent', $extConf['useragent']);

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

            }
            // Turn off libxml's error logging.
            $libxmlErrors = libxml_use_internal_errors(TRUE);
            // Disables the functionality to allow external entities to be loaded when parsing the XML, must be kept
            $previousValueOfEntityLoader = libxml_disable_entity_loader(TRUE);
            // Load XML from file.
            $xml = simplexml_load_string(\TYPO3\CMS\Core\Utility\GeneralUtility::getUrl($location));

It seems like TYPO3\CMS\Core\Utility\GeneralUtility::getUrl($location) can also be of type false; however, parameter $data of simplexml_load_string() does only seem to accept string, maybe add an additional type check?

            // reset entity loader setting
            libxml_disable_entity_loader($previousValueOfEntityLoader);
            // Reset libxml's error logging.
            libxml_use_internal_errors($libxmlErrors);
            // Set some basic properties.
            if ($xml !== FALSE) {
                $this->xml = $xml;
                return TRUE;
            } else {
                Helper::devLog('Could not load XML file from "'.$location.'"', DEVLOG_SEVERITY_ERROR);
            }
        } else {
            Helper::devLog('Invalid file location "'.$location.'" for document loading', DEVLOG_SEVERITY_ERROR);
        }
        return FALSE;
    }

    /**
     * Register all available data formats
     *
     * @access protected
     *
     * @return void
     */
    protected function loadFormats() {
        if (!$this->formatsLoaded) {
            // Get available data formats from database.
            $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
                'tx_dlf_formats.type AS type,tx_dlf_formats.root AS root,tx_dlf_formats.namespace AS namespace,tx_dlf_formats.class AS class',
                'tx_dlf_formats',
                'tx_dlf_formats.pid=0'
                    .Helper::whereClause('tx_dlf_formats'),
                '',
                '',
                ''
            );
            while ($resArray = $GLOBALS['TYPO3_DB']->sql_fetch_assoc($result)) {
                // Update format registry.
                $this->formats[$resArray['type']] = [
                    'rootElement' => $resArray['root'],
                    'namespaceURI' => $resArray['namespace'],
                    'class' => $resArray['class']
                ];
            }
            $this->formatsLoaded = TRUE;
        }
    }

    /**
     * Register all available namespaces for a \SimpleXMLElement object
     *
     * @access public
     *
     * @param \SimpleXMLElement|\DOMXPath &$obj: \SimpleXMLElement or \DOMXPath object
     *
     * @return void
     */
    public function registerNamespaces(&$obj) {
        $this->loadFormats();
        // Do we have a \SimpleXMLElement or \DOMXPath object?
        if ($obj instanceof \SimpleXMLElement) {
            $method = 'registerXPathNamespace';
        } elseif ($obj instanceof \DOMXPath) {
            $method = 'registerNamespace';
        } else {
            Helper::devLog('Given object is neither a SimpleXMLElement nor a DOMXPath instance', DEVLOG_SEVERITY_ERROR);
            return;
        }
        // Register metadata format's namespaces.
        foreach ($this->formats as $enc => $conf) {
            $obj->$method(strtolower($enc), $conf['namespaceURI']);
        }
    }

    /**
     * This saves the document to the database and index
     *
     * @access public
     *
     * @param integer $pid: The PID of the saved record
     * @param integer $core: The UID of the Solr core for indexing
     *
     * @return boolean TRUE on success or FALSE on failure
     */
    public function save($pid = 0, $core = 0) {
        if (TYPO3_MODE !== 'BE') {

The condition Kitodo\Dlf\Common\TYPO3_MODE !== 'BE' is always false.

            Helper::devLog('Saving a document is only allowed in the backend', DEVLOG_SEVERITY_ERROR);
            return FALSE;
        }
        // Make sure $pid is a non-negative integer.
        $pid = max(intval($pid), 0);
        // Make sure $core is a non-negative integer.
        $core = max(intval($core), 0);
        // If $pid is not given, try to get it elsewhere.
        if (!$pid
            && $this->pid) {
            // Retain current PID.
            $pid = $this->pid;
        } elseif (!$pid) {
            Helper::devLog('Invalid PID '.$pid.' for document saving', DEVLOG_SEVERITY_ERROR);
            return FALSE;
        }
        // Set PID for metadata definitions.
        $this->cPid = $pid;
        // Set UID placeholder if not updating existing record.
        if ($pid != $this->pid) {
            $this->uid = uniqid('NEW');
        }
        // Get metadata array.
        $metadata = $this->getTitledata($pid);
        // Check for record identifier.
        if (empty($metadata['record_id'][0])) {
            Helper::devLog('No record identifier found to avoid duplication', DEVLOG_SEVERITY_ERROR);
            return FALSE;
        }
        // Load plugin configuration.
        $conf = unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf'][self::$extKey]);
        // Get UID for user "_cli_dlf".
        $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
            'be_users.uid AS uid',
            'be_users',
            'username='.$GLOBALS['TYPO3_DB']->fullQuoteStr('_cli_dlf', 'be_users')
                .\TYPO3\CMS\Backend\Utility\BackendUtility::BEenableFields('be_users')
                .\TYPO3\CMS\Backend\Utility\BackendUtility::deleteClause('be_users'),
            '',
            '',
            '1'
        );
        if (!$GLOBALS['TYPO3_DB']->sql_num_rows($result)) {
            Helper::devLog('Backend user "_cli_dlf" not found or disabled', DEVLOG_SEVERITY_ERROR);
            return FALSE;
        }
        // Get UID for structure type.
        $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
            'tx_dlf_structures.uid AS uid',
            'tx_dlf_structures',
            'tx_dlf_structures.pid='.intval($pid)
                .' AND tx_dlf_structures.index_name='.$GLOBALS['TYPO3_DB']->fullQuoteStr($metadata['type'][0], 'tx_dlf_structures')
                .Helper::whereClause('tx_dlf_structures'),
            '',
            '',
            '1'
        );
        if ($GLOBALS['TYPO3_DB']->sql_num_rows($result)) {
            list ($structure) = $GLOBALS['TYPO3_DB']->sql_fetch_row($result);
        } else {
            Helper::devLog('Could not identify document/structure type "'.$GLOBALS['TYPO3_DB']->fullQuoteStr($metadata['type'][0], 'tx_dlf_structures').'"', DEVLOG_SEVERITY_ERROR);
            return FALSE;
        }
        $metadata['type'][0] = $structure;
        // Get UIDs for collections.
        $collections = [];
        $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
            'tx_dlf_collections.index_name AS index_name,tx_dlf_collections.uid AS uid',
            'tx_dlf_collections',
            'tx_dlf_collections.pid='.intval($pid)
                .' AND tx_dlf_collections.sys_language_uid IN (-1,0)'
                .Helper::whereClause('tx_dlf_collections'),
            '',
            '',
            ''
        );
        while ($resArray = $GLOBALS['TYPO3_DB']->sql_fetch_assoc($result)) {
            $collUid[$resArray['index_name']] = $resArray['uid'];
        }
        foreach ($metadata['collection'] as $collection) {
            if (!empty($collUid[$collection])) {
                // Add existing collection's UID.
                $collections[] = $collUid[$collection];

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

            } else {
                // Insert new collection.
                $collNewUid = uniqid('NEW');
                $collData['tx_dlf_collections'][$collNewUid] = [
                    'pid' => $pid,
                    'label' => $collection,
                    'index_name' => $collection,
                    'oai_name' => (!empty($conf['publishNewCollections']) ? Helper::getCleanString($collection) : ''),
                    'description' => '',
                    'documents' => 0,
                    'owner' => 0,
                    'status' => 0,
                ];
                $substUid = Helper::processDB($collData);
                // Prevent double insertion.
                unset ($collData);
                // Add new collection's UID.
                $collections[] = $substUid[$collNewUid];
                if ((TYPO3_REQUESTTYPE & TYPO3_REQUESTTYPE_CLI) == FALSE) {

It seems like you are loosely comparing Kitodo\Dlf\Common\TYPO3_REQUESTTYPE & Kitodo\Dlf\Common\TYPO3_REQUESTTYPE_CLI of type integer to the boolean FALSE. If you are specifically checking for 0, consider using something more explicit like === 0 instead.

                    Helper::addMessage(
                        htmlspecialchars(sprintf(Helper::getMessage('flash.newCollection'), $collection, $substUid[$collNewUid])),
                        Helper::getMessage('flash.attention', TRUE),
                        \TYPO3\CMS\Core\Messaging\FlashMessage::INFO,
                        TRUE
                    );
                }
            }
        }
        $metadata['collection'] = $collections;
        // Get UID for owner.
        $owner = !empty($metadata['owner'][0]) ? $metadata['owner'][0] : 'default';
        $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
            'tx_dlf_libraries.uid AS uid',
            'tx_dlf_libraries',
            'tx_dlf_libraries.pid='.intval($pid)
                .' AND tx_dlf_libraries.index_name='.$GLOBALS['TYPO3_DB']->fullQuoteStr($owner, 'tx_dlf_libraries')
                .Helper::whereClause('tx_dlf_libraries'),
            '',
            '',
            '1'
        );
        if ($GLOBALS['TYPO3_DB']->sql_num_rows($result)) {
            list ($ownerUid) = $GLOBALS['TYPO3_DB']->sql_fetch_row($result);
        } else {
            // Insert new library.
            $libNewUid = uniqid('NEW');
            $libData['tx_dlf_libraries'][$libNewUid] = [

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

                'pid' => $pid,
                'label' => $owner,
                'index_name' => $owner,
                'website' => '',
                'contact' => '',
                'image' => '',
                'oai_label' => '',
                'oai_base' => '',
                'opac_label' => '',
                'opac_base' => '',
                'union_label' => '',
                'union_base' => '',
            ];
            $substUid = Helper::processDB($libData);
            // Add new library's UID.
            $ownerUid = $substUid[$libNewUid];
            if ((TYPO3_REQUESTTYPE & TYPO3_REQUESTTYPE_CLI) == FALSE) {

It seems like you are loosely comparing Kitodo\Dlf\Common\TYPO3_REQUESTTYPE & Kitodo\Dlf\Common\TYPO3_REQUESTTYPE_CLI of type integer to the boolean FALSE. If you are specifically checking for 0, consider using something more explicit like === 0 instead.

                Helper::addMessage(
                    htmlspecialchars(sprintf(Helper::getMessage('flash.newLibrary'), $owner, $ownerUid)),
                    Helper::getMessage('flash.attention', TRUE),
                    \TYPO3\CMS\Core\Messaging\FlashMessage::INFO,
                    TRUE
                );
            }
        }
        $metadata['owner'][0] = $ownerUid;
        // Get UID of parent document.
        $partof = 0;
        // Get the closest ancestor of the current document which has a MPTR child.
        $parentMptr = $this->mets->xpath('./mets:structMap[@TYPE="LOGICAL"]//mets:div[@ID="'.$this->_getToplevelId().'"]/ancestor::mets:div[./mets:mptr][1]/mets:mptr');
        if (!empty($parentMptr[0])) {
            $parentLocation = (string) $parentMptr[0]->attributes('http://www.w3.org/1999/xlink')->href;
            if ($parentLocation != $this->location) {
                $parentDoc = self::getInstance($parentLocation, $pid);
                if ($parentDoc->ready) {
                    if ($parentDoc->pid != $pid) {
                        $parentDoc->save($pid, $core);
                    }
                    $partof = $parentDoc->uid;
                }
            }
        }
        // Use the date of publication or title as alternative sorting metric for parts of multi-part works.
        if (!empty($partof)) {
            if (empty($metadata['volume'][0])
                && !empty($metadata['year'][0])) {
                $metadata['volume'] = $metadata['year'];
            }
            if (empty($metadata['volume_sorting'][0])) {
                if (!empty($metadata['year_sorting'][0])) {
                    $metadata['volume_sorting'][0] = $metadata['year_sorting'][0];
                } elseif (!empty($metadata['year'][0])) {
                    $metadata['volume_sorting'][0] = $metadata['year'][0];
                }
            }
            // If volume_sorting is still empty, try to use title_sorting finally (workaround for newspapers)
            if (empty($metadata['volume_sorting'][0])) {
                if (!empty($metadata['title_sorting'][0])) {
                    $metadata['volume_sorting'][0] = $metadata['title_sorting'][0];
                }
            }
        }
        // Get metadata for lists and sorting.
        $listed = [];
        $sortable = [];
        $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
            'tx_dlf_metadata.index_name AS index_name,tx_dlf_metadata.is_listed AS is_listed,tx_dlf_metadata.is_sortable AS is_sortable',
            'tx_dlf_metadata',
            '(tx_dlf_metadata.is_listed=1 OR tx_dlf_metadata.is_sortable=1)'
                .' AND tx_dlf_metadata.pid='.intval($pid)
                .Helper::whereClause('tx_dlf_metadata'),
            '',
            '',
            ''
        );
        while ($resArray = $GLOBALS['TYPO3_DB']->sql_fetch_assoc($result)) {
            if (!empty($metadata[$resArray['index_name']])) {
                if ($resArray['is_listed']) {
                    $listed[$resArray['index_name']] = $metadata[$resArray['index_name']];
                }
                if ($resArray['is_sortable']) {
                    $sortable[$resArray['index_name']] = $metadata[$resArray['index_name']][0];
                }
            }
        }
        // Fill data array.
        $data['tx_dlf_documents'][$this->uid] = [

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

            'pid' => $pid,
            $GLOBALS['TCA']['tx_dlf_documents']['ctrl']['enablecolumns']['starttime'] => 0,
            $GLOBALS['TCA']['tx_dlf_documents']['ctrl']['enablecolumns']['endtime'] => 0,
            'prod_id' => $metadata['prod_id'][0],
            'location' => $this->location,
            'record_id' => $metadata['record_id'][0],
            'opac_id' => $metadata['opac_id'][0],
            'union_id' => $metadata['union_id'][0],
            'urn' => $metadata['urn'][0],
            'purl' => $metadata['purl'][0],
            'title' => $metadata['title'][0],
            'title_sorting' => $metadata['title_sorting'][0],
            'author' => implode('; ', $metadata['author']),
            'year' => implode('; ', $metadata['year']),
            'place' => implode('; ', $metadata['place']),
            'thumbnail' => $this->_getThumbnail(TRUE),
            'metadata' => serialize($listed),
            'metadata_sorting' => serialize($sortable),
            'structure' => $metadata['type'][0],
            'partof' => $partof,
            'volume' => $metadata['volume'][0],
            'volume_sorting' => $metadata['volume_sorting'][0],
            'collections' => $metadata['collection'],
            'owner' => $metadata['owner'][0],
            'solrcore' => $core,
            'status' => 0,
        ];
        // Unhide hidden documents.
        if (!empty($conf['unhideOnIndex'])) {
            $data['tx_dlf_documents'][$this->uid][$GLOBALS['TCA']['tx_dlf_documents']['ctrl']['enablecolumns']['disabled']] = 0;
        }
        // Process data.
        $newIds = Helper::processDB($data);
        // Replace placeholder with actual UID.
        if (strpos($this->uid, 'NEW') === 0) {
            $this->uid = $newIds[$this->uid];
            $this->pid = $pid;
            $this->parentId = $partof;
        }
        if ((TYPO3_REQUESTTYPE & TYPO3_REQUESTTYPE_CLI) == FALSE) {

It seems like you are loosely comparing Kitodo\Dlf\Common\TYPO3_REQUESTTYPE & Kitodo\Dlf\Common\TYPO3_REQUESTTYPE_CLI of type integer to the boolean FALSE. If you are specifically checking for 0, consider using something more explicit like === 0 instead.

            Helper::addMessage(
                htmlspecialchars(sprintf(Helper::getMessage('flash.documentSaved'), $metadata['title'][0], $this->uid)),
                Helper::getMessage('flash.done', TRUE),
                \TYPO3\CMS\Core\Messaging\FlashMessage::OK,
                TRUE
            );
        }
        // Add document to index.
        if ($core) {
            Indexer::add($this, $core);
        } else {
            Helper::devLog('Invalid UID "'.$core.'" for Solr core', DEVLOG_SEVERITY_NOTICE);
        }
        return TRUE;
    }

    /**
     * This returns $this->cPid via __get()
     *
     * @access protected
     *
     * @return integer The PID of the metadata definitions
     */
    protected function _getCPid() {
        return $this->cPid;
    }

    /**
     * This builds an array of the document's dmdSecs
     *
     * @access protected
     *
     * @return array Array of dmdSecs with their IDs as array key
     */
    protected function _getDmdSec() {
        if (!$this->dmdSecLoaded) {
            // Get available data formats.
            $this->loadFormats();
            // Get dmdSec nodes from METS.
            $dmdIds = $this->mets->xpath('./mets:dmdSec/@ID');
            foreach ($dmdIds as $dmdId) {
                if ($type = $this->mets->xpath('./mets:dmdSec[@ID="'.(string) $dmdId.'"]/mets:mdWrap[not(@MDTYPE="OTHER")]/@MDTYPE')) {
                    if (!empty($this->formats[(string) $type[0]])) {
                        $type = (string) $type[0];
                        $xml = $this->mets->xpath('./mets:dmdSec[@ID="'.(string) $dmdId.'"]/mets:mdWrap[@MDTYPE="'.$type.'"]/mets:xmlData/'.strtolower($type).':'.$this->formats[$type]['rootElement']);
                    }
                } elseif ($type = $this->mets->xpath('./mets:dmdSec[@ID="'.(string) $dmdId.'"]/mets:mdWrap[@MDTYPE="OTHER"]/@OTHERMDTYPE')) {
                    if (!empty($this->formats[(string) $type[0]])) {
                        $type = (string) $type[0];
                        $xml = $this->mets->xpath('./mets:dmdSec[@ID="'.(string) $dmdId.'"]/mets:mdWrap[@MDTYPE="OTHER"][@OTHERMDTYPE="'.$type.'"]/mets:xmlData/'.strtolower($type).':'.$this->formats[$type]['rootElement']);
                    }
                }
                if ($xml) {

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

                    $this->dmdSec[(string) $dmdId]['type'] = $type;
                    $this->dmdSec[(string) $dmdId]['xml'] = $xml[0];
                    $this->registerNamespaces($this->dmdSec[(string) $dmdId]['xml']);
                }
            }
            $this->dmdSecLoaded = TRUE;
        }
        return $this->dmdSec;
    }

    /**
     * This builds the file ID -> USE concordance
     *
     * @access protected
     *
     * @return array Array of file use groups with file IDs
     */
    protected function _getFileGrps() {
        if (!$this->fileGrpsLoaded) {
            // Get configured USE attributes.
            $extConf = unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf'][self::$extKey]);
            $useGrps = \TYPO3\CMS\Core\Utility\GeneralUtility::trimExplode(',', $extConf['fileGrps']);
            if (!empty($extConf['fileGrpThumbs'])) {
                $useGrps[] = $extConf['fileGrpThumbs'];
            }
            if (!empty($extConf['fileGrpDownload'])) {
                $useGrps[] = $extConf['fileGrpDownload'];
            }
            if (!empty($extConf['fileGrpFulltext'])) {
                $useGrps[] = $extConf['fileGrpFulltext'];
            }
            if (!empty($extConf['fileGrpAudio'])) {
                $useGrps[] = $extConf['fileGrpAudio'];
            }
            // Get all file groups.
            $fileGrps = $this->mets->xpath('./mets:fileSec/mets:fileGrp');
            // Build concordance for configured USE attributes.
            foreach ($fileGrps as $fileGrp) {
                if (in_array((string) $fileGrp['USE'], $useGrps)) {
                    foreach ($fileGrp->children('http://www.loc.gov/METS/')->file as $file) {
                        $this->fileGrps[(string) $file->attributes()->ID] = (string) $fileGrp['USE'];
                    }
                }
            }
            // Are there any fulltext files available?
            if (!empty($extConf['fileGrpFulltext'])
                && in_array($extConf['fileGrpFulltext'], $this->fileGrps)) {
                $this->hasFulltext = TRUE;
            }
            $this->fileGrpsLoaded = TRUE;
        }
        return $this->fileGrps;
    }

    /**
     * This returns $this->hasFulltext via __get()
     *
     * @access protected
     *
     * @return boolean Are there any fulltext files available?
     */
    protected function _getHasFulltext() {
        // Are the fileGrps already loaded?
        if (!$this->fileGrpsLoaded) {
            $this->_getFileGrps();
        }
        return $this->hasFulltext;
    }

    /**
     * This returns $this->location via __get()
     *
     * @access protected
     *
     * @return string The location of the document
     */
    protected function _getLocation() {
        return $this->location;
    }

    /**
     * This builds an array of the document's metadata
     *
     * @access protected
     *
     * @return array Array of metadata with their corresponding logical structure node ID as key
     */
    protected function _getMetadataArray() {
        // Set metadata definitions' PID.
        $cPid = ($this->cPid ? $this->cPid : $this->pid);
        if (!$cPid) {
            Helper::devLog('Invalid PID '.$cPid.' for metadata definitions', DEVLOG_SEVERITY_ERROR);
            return [];
        }
        if (!$this->metadataArrayLoaded
            || $this->metadataArray[0] != $cPid) {
            // Get all logical structure nodes with metadata.
            if (($ids = $this->mets->xpath('./mets:structMap[@TYPE="LOGICAL"]//mets:div[@DMDID]/@ID'))) {
                foreach ($ids as $id) {
                    $this->metadataArray[(string) $id] = $this->getMetadata((string) $id, $cPid);
                }
            }
            // Set current PID for metadata definitions.
            $this->metadataArray[0] = $cPid;
            $this->metadataArrayLoaded = TRUE;
        }
        return $this->metadataArray;
    }

    /**
     * This returns $this->mets via __get()
     *
     * @access protected
     *
     * @return \SimpleXMLElement The XML's METS part as \SimpleXMLElement object
     */
    protected function _getMets() {
        return $this->mets;
    }

    /**
     * This returns $this->numPages via __get()
     *
     * @access protected
     *
     * @return integer The total number of pages and/or tracks
     */
    protected function _getNumPages() {
        $this->_getPhysicalStructure();
        return $this->numPages;
    }

    /**
     * This returns $this->parentId via __get()
     *
     * @access protected
     *
     * @return integer The UID of the parent document or zero if not applicable
     */
    protected function _getParentId() {
        return $this->parentId;
    }

    /**
     * This builds an array of the document's physical structure
     *
     * @access protected
     *
     * @return array Array of physical elements' id, type, label and file representations ordered by @ORDER attribute
     */
    protected function _getPhysicalStructure() {
        // Is there no physical structure array yet?
        if (!$this->physicalStructureLoaded) {
            // Does the document have a structMap node of type "PHYSICAL"?
            $elementNodes = $this->mets->xpath('./mets:structMap[@TYPE="PHYSICAL"]/mets:div[@TYPE="physSequence"]/mets:div');
            if ($elementNodes) {

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

                // Get file groups.
                $fileUse = $this->_getFileGrps();
                // Get the physical sequence's metadata.
                $physNode = $this->mets->xpath('./mets:structMap[@TYPE="PHYSICAL"]/mets:div[@TYPE="physSequence"]');
                $physSeq[0] = (string) $physNode[0]['ID'];

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

                $this->physicalStructureInfo[$physSeq[0]]['id'] = (string) $physNode[0]['ID'];
                $this->physicalStructureInfo[$physSeq[0]]['dmdId'] = (isset($physNode[0]['DMDID']) ? (string) $physNode[0]['DMDID'] : '');
                $this->physicalStructureInfo[$physSeq[0]]['label'] = (isset($physNode[0]['LABEL']) ? (string) $physNode[0]['LABEL'] : '');
                $this->physicalStructureInfo[$physSeq[0]]['orderlabel'] = (isset($physNode[0]['ORDERLABEL']) ? (string) $physNode[0]['ORDERLABEL'] : '');
                $this->physicalStructureInfo[$physSeq[0]]['type'] = (string) $physNode[0]['TYPE'];
                $this->physicalStructureInfo[$physSeq[0]]['contentIds'] = (isset($physNode[0]['CONTENTIDS']) ? (string) $physNode[0]['CONTENTIDS'] : '');
                // Get the file representations from fileSec node.
                foreach ($physNode[0]->children('http://www.loc.gov/METS/')->fptr as $fptr) {
                    // Check if file has valid @USE attribute.
                    if (!empty($fileUse[(string) $fptr->attributes()->FILEID])) {
                        $this->physicalStructureInfo[$physSeq[0]]['files'][$fileUse[(string) $fptr->attributes()->FILEID]] = (string) $fptr->attributes()->FILEID;
                    }
                }
                // Build the physical elements' array from the physical structMap node.
                foreach ($elementNodes as $elementNode) {
                    $elements[(int) $elementNode['ORDER']] = (string) $elementNode['ID'];
                    $this->physicalStructureInfo[$elements[(int) $elementNode['ORDER']]]['id'] = (string) $elementNode['ID'];

The variable $elements seems to be defined later in this foreach loop on line 1527. Are you sure it is defined here?

                    $this->physicalStructureInfo[$elements[(int) $elementNode['ORDER']]]['dmdId'] = (isset($elementNode['DMDID']) ? (string) $elementNode['DMDID'] : '');
                    $this->physicalStructureInfo[$elements[(int) $elementNode['ORDER']]]['label'] = (isset($elementNode['LABEL']) ? (string) $elementNode['LABEL'] : '');
                    $this->physicalStructureInfo[$elements[(int) $elementNode['ORDER']]]['orderlabel'] = (isset($elementNode['ORDERLABEL']) ? (string) $elementNode['ORDERLABEL'] : '');
                    $this->physicalStructureInfo[$elements[(int) $elementNode['ORDER']]]['type'] = (string) $elementNode['TYPE'];
                    $this->physicalStructureInfo[$elements[(int) $elementNode['ORDER']]]['contentIds'] = (isset($elementNode['CONTENTIDS']) ? (string) $elementNode['CONTENTIDS'] : '');
                    // Get the file representations from fileSec node.
                    foreach ($elementNode->children('http://www.loc.gov/METS/')->fptr as $fptr) {
                        // Check if file has valid @USE attribute.
                        if (!empty($fileUse[(string) $fptr->attributes()->FILEID])) {
                            $this->physicalStructureInfo[$elements[(int) $elementNode['ORDER']]]['files'][$fileUse[(string) $fptr->attributes()->FILEID]] = (string) $fptr->attributes()->FILEID;
                        }
                    }
                }
                // Sort array by keys (= @ORDER).
                if (ksort($elements)) {
                    // Set total number of pages/tracks.
                    $this->numPages = count($elements);
                    // Merge and re-index the array to get nice numeric indexes.
                    $this->physicalStructure = array_merge($physSeq, $elements);
                }
            }
            $this->physicalStructureLoaded = TRUE;
        }
        return $this->physicalStructure;
    }

    /**
     * This gives an array of the document's physical structure metadata
     *
     * @access protected
     *
     * @return array Array of elements' type, label and file representations ordered by @ID attribute
     */
    protected function _getPhysicalStructureInfo() {
        // Is there no physical structure array yet?
        if (!$this->physicalStructureLoaded) {
            // Build physical structure array.
            $this->_getPhysicalStructure();
        }
        return $this->physicalStructureInfo;
    }

    /**
     * This returns $this->pid via __get()
     *
     * @access protected
     *
     * @return integer The PID of the document or zero if not in database
     */
    protected function _getPid() {
        return $this->pid;
    }

    /**
     * This returns $this->ready via __get()
     *
     * @access protected
     *
     * @return boolean Is the document instantiated successfully?
     */
    protected function _getReady() {
        return $this->ready;
    }

    /**
     * This returns $this->recordId via __get()
     *
     * @access protected
     *
     * @return mixed The METS file's record identifier
     */
    protected function _getRecordId() {
        return $this->recordId;
    }

    /**
     * This returns $this->rootId via __get()
     *
     * @access protected
     *
     * @return integer The UID of the root document or zero if not applicable
     */
    protected function _getRootId() {
        if (!$this->rootIdLoaded) {
            if ($this->parentId) {
                $parent = self::getInstance($this->parentId, $this->pid);
                $this->rootId = $parent->rootId;
            }
            $this->rootIdLoaded = TRUE;
        }
        return $this->rootId;
    }

    /**
     * This returns the smLinks between logical and physical structMap
     *
     * @access protected
     *
     * @return array The links between logical and physical nodes
     */
    protected function _getSmLinks() {
        if (!$this->smLinksLoaded) {
            $smLinks = $this->mets->xpath('./mets:structLink/mets:smLink');
            foreach ($smLinks as $smLink) {
                $this->smLinks['l2p'][(string) $smLink->attributes('http://www.w3.org/1999/xlink')->from][] = (string) $smLink->attributes('http://www.w3.org/1999/xlink')->to;
                $this->smLinks['p2l'][(string) $smLink->attributes('http://www.w3.org/1999/xlink')->to][] = (string) $smLink->attributes('http://www.w3.org/1999/xlink')->from;
            }
            $this->smLinksLoaded = TRUE;
        }
        return $this->smLinks;
    }

    /**
     * This builds an array of the document's logical structure
     *
     * @access protected
     *
     * @return array Array of structure nodes' id, label, type and physical page indexes/mptr link with original hierarchy preserved
     */
    protected function _getTableOfContents() {
        // Is there no logical structure array yet?
        if (!$this->tableOfContentsLoaded) {
            // Get all logical structures.
            $this->getLogicalStructure('', TRUE);
            $this->tableOfContentsLoaded = TRUE;
        }
        return $this->tableOfContents;
    }

    /**
     * This returns the document's thumbnail location
     *
     * @access protected
     *
     * @param boolean $forceReload: Force reloading the thumbnail instead of returning the cached value
     *
     * @return string The document's thumbnail location
     */
    protected function _getThumbnail($forceReload = FALSE) {
        if (!$this->thumbnailLoaded
            || $forceReload) {
            // Retain current PID.
            $cPid = ($this->cPid ? $this->cPid : $this->pid);
            if (!$cPid) {
                Helper::devLog('Invalid PID '.$cPid.' for structure definitions', DEVLOG_SEVERITY_ERROR);
                $this->thumbnailLoaded = TRUE;
                return $this->thumbnail;
            }
            // Load extension configuration.
            $extConf = unserialize($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf'][self::$extKey]);
            if (empty($extConf['fileGrpThumbs'])) {
                Helper::devLog('No fileGrp for thumbnails specified', DEVLOG_SEVERITY_WARNING);
                $this->thumbnailLoaded = TRUE;
                return $this->thumbnail;
            }
            $strctId = $this->_getToplevelId();
            $metadata = $this->getTitledata($cPid);
            // Get structure element to get thumbnail from.
            $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
                'tx_dlf_structures.thumbnail AS thumbnail',
                'tx_dlf_structures',
                'tx_dlf_structures.pid='.intval($cPid)
                    .' AND tx_dlf_structures.index_name='.$GLOBALS['TYPO3_DB']->fullQuoteStr($metadata['type'][0], 'tx_dlf_structures')
                    .Helper::whereClause('tx_dlf_structures'),
                '',
                '',
                '1'
            );
            if ($GLOBALS['TYPO3_DB']->sql_num_rows($result) > 0) {
                $resArray = $GLOBALS['TYPO3_DB']->sql_fetch_assoc($result);
                // Get desired thumbnail structure if not the toplevel structure itself.
                if (!empty($resArray['thumbnail'])) {
                    $strctType = Helper::getIndexNameFromUid($resArray['thumbnail'], 'tx_dlf_structures', $cPid);
                    // Check if this document has a structure element of the desired type.
                    $strctIds = $this->mets->xpath('./mets:structMap[@TYPE="LOGICAL"]//mets:div[@TYPE="'.$strctType.'"]/@ID');
                    if (!empty($strctIds)) {
                        $strctId = (string) $strctIds[0];
                    }
                }
                // Load smLinks.
                $this->_getSmLinks();
                // Get thumbnail location.
                if ($this->_getPhysicalStructure()
                    && !empty($this->smLinks['l2p'][$strctId])) {
                    $this->thumbnail = $this->getFileLocation($this->physicalStructureInfo[$this->smLinks['l2p'][$strctId][0]]['files'][$extConf['fileGrpThumbs']]);
                } else {
                    $this->thumbnail = $this->getFileLocation($this->physicalStructureInfo[$this->physicalStructure[1]]['files'][$extConf['fileGrpThumbs']]);
                }
            } else {
                Helper::devLog('No structure of type "'.$metadata['type'][0].'" found in database', DEVLOG_SEVERITY_ERROR);
            }
            $this->thumbnailLoaded = TRUE;
        }
        return $this->thumbnail;
    }

    /**
     * This returns the ID of the toplevel logical structure node
     *
     * @access protected
     *
     * @return string The logical structure node's ID
     */
    protected function _getToplevelId() {
        if (empty($this->toplevelId)) {
            // Get all logical structure nodes with metadata, but without associated METS-Pointers.
            if (($divs = $this->mets->xpath('./mets:structMap[@TYPE="LOGICAL"]//mets:div[@DMDID and not(./mets:mptr)]'))) {
                // Load smLinks.
                $this->_getSmLinks();
                foreach ($divs as $div) {
                    $id = (string) $div['ID'];
                    // Are there physical structure nodes for this logical structure?
                    if (array_key_exists($id, $this->smLinks['l2p'])) {
                        // Yes. That's what we're looking for.
                        $this->toplevelId = $id;
                        break;
                    } elseif (empty($this->toplevelId)) {
                        // No. Remember this anyway, but keep looking for a better one.
                        $this->toplevelId = $id;
                    }
                }
            }
        }
        return $this->toplevelId;
    }

    /**
     * This returns $this->uid via __get()
     *
     * @access protected
     *
     * @return mixed The UID or the URL of the document
     */
    protected function _getUid() {
        return $this->uid;
    }

    /**
     * This sets $this->cPid via __set()
     *
     * @access protected
     *
     * @param integer $value: The new PID for the metadata definitions
     *
     * @return void
     */
    protected function _setCPid($value) {
        $this->cPid = max(intval($value), 0);
    }

    /**
     * This magic method is invoked each time a clone is called on the object variable
     * (This method is defined as private/protected because singleton objects should not be cloned)
     *
     * @access protected
     *
     * @return void
     */
    protected function __clone() {}

    /**
     * This is a singleton class, thus the constructor should be private/protected
     * (Get an instance of this class by calling \Kitodo\Dlf\Common\Document::getInstance())
     *
     * @access protected
     *
     * @param integer $uid: The UID of the document to parse or URL to XML file
     * @param integer $pid: If > 0, then only document with this PID gets loaded
     *
     * @return void
     */
    protected function __construct($uid, $pid) {
        // Prepare to check database for the requested document.
        if (\TYPO3\CMS\Core\Utility\MathUtility::canBeInterpretedAsInteger($uid)) {
            $whereClause = 'tx_dlf_documents.uid='.intval($uid).Helper::whereClause('tx_dlf_documents');
        } else {
            // Try to load METS file.
            if (\TYPO3\CMS\Core\Utility\GeneralUtility::isValidUrl($uid)
                && $this->load($uid)) {
                // Initialize core METS object.
                $this->init();
                if ($this->mets !== NULL) {
                    // Cast to string for safety reasons.
                    $location = (string) $uid;
                    // Check for METS object @ID.
                    if (!empty($this->mets['OBJID'])) {
                        $this->recordId = (string) $this->mets['OBJID'];
                    }
                    // Get hook objects.
                    $hookObjects = Helper::getHookObjects('Classes/Common/Document.php');
                    // Apply hooks.
                    foreach ($hookObjects as $hookObj) {
                        if (method_exists($hookObj, 'construct_postProcessRecordId')) {
                            $hookObj->construct_postProcessRecordId($this->xml, $this->recordId);
                        }
                    }
                } else {
                    // No METS part found.
                    return;
                }
            } else {
                // Loading failed.
                return;
            }
            if (!empty($location)
                && !empty($this->recordId)) {
                // Try to match record identifier or location (both should be unique).
                $whereClause = '(tx_dlf_documents.location='.$GLOBALS['TYPO3_DB']->fullQuoteStr($location, 'tx_dlf_documents').' OR tx_dlf_documents.record_id='.$GLOBALS['TYPO3_DB']->fullQuoteStr($this->recordId, 'tx_dlf_documents').')'.Helper::whereClause('tx_dlf_documents');
            } else {
                // Can't persistently identify document, don't try to match at all.
                $whereClause = '1=-1';
            }
        }
        // Check for PID if needed.
        if ($pid) {
            $whereClause .= ' AND tx_dlf_documents.pid='.intval($pid);
        }
        // Get document PID and location from database.
        $result = $GLOBALS['TYPO3_DB']->exec_SELECTquery(
            'tx_dlf_documents.uid AS uid,tx_dlf_documents.pid AS pid,tx_dlf_documents.record_id AS record_id,tx_dlf_documents.partof AS partof,tx_dlf_documents.thumbnail AS thumbnail,tx_dlf_documents.location AS location',
            'tx_dlf_documents',
            $whereClause,
            '',
            '',
            '1'
        );
        if ($GLOBALS['TYPO3_DB']->sql_num_rows($result) > 0) {
            list ($this->uid, $this->pid, $this->recordId, $this->parentId, $this->thumbnail, $this->location) = $GLOBALS['TYPO3_DB']->sql_fetch_row($result);
            $this->thumbnailLoaded = TRUE;
            // Load XML file if necessary...
            if ($this->mets === NULL
                && $this->load($this->location)) {
                // ...and set some basic properties.
                $this->init();
            }
            // Do we have a METS object now?
            if ($this->mets !== NULL) {
                // Set new location if necessary.
                if (!empty($location)) {
                    $this->location = $location;
                }
                // Document ready!
                $this->ready = TRUE;
            }
        } elseif ($this->mets !== NULL) {
            // Set location as UID for documents not in database.
            $this->uid = $location;

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

            $this->location = $location;
            // Document ready!
            $this->ready = TRUE;
        } else {
            Helper::devLog('No document with UID '.$uid.' found or document not accessible', DEVLOG_SEVERITY_ERROR);
        }
    }

    /**
     * This magic method is called each time an invisible property is referenced from the object
     *
     * @access public
     *
     * @param string $var: Name of variable to get
     *
     * @return mixed Value of $this->$var
     */
    public function __get($var) {
        $method = '_get'.ucfirst($var);
        if (!property_exists($this, $var)
            || !method_exists($this, $method)) {
            Helper::devLog('There is no getter function for property "'.$var.'"', DEVLOG_SEVERITY_WARNING);
            return;
        } else {
            return $this->$method();
        }
    }

    /**
     * This magic method is called each time an invisible property is referenced from the object
     *
     * @access public
     *
     * @param string $var: Name of variable to set
     * @param mixed $value: New value of variable
     *
     * @return void
     */
    public function __set($var, $value) {
        $method = '_set'.ucfirst($var);
        if (!property_exists($this, $var)
            || !method_exists($this, $method)) {
            Helper::devLog('There is no setter function for property "'.$var.'"', DEVLOG_SEVERITY_WARNING);
        } else {
            $this->$method($value);
        }
    }

    /**
     * This magic method is executed prior to any serialization of the object
     * @see __wakeup()
     *
     * @access public
     *
     * @return array Properties to be serialized
     */
    public function __sleep() {
        // \SimpleXMLElement objects can't be serialized, thus save the XML as string for serialization
        $this->asXML = $this->xml->asXML();
        return ['uid', 'pid', 'recordId', 'parentId', 'asXML'];
    }

    /**
     * This magic method is used for setting a string value for the object
     *
     * @access public
     *
     * @return string String representing the METS object
     */
    public function __toString() {
        $xml = new \DOMDocument('1.0', 'utf-8');
        $xml->appendChild($xml->importNode(dom_import_simplexml($this->mets), TRUE));
        $xml->formatOutput = TRUE;
        return $xml->saveXML();
    }

    /**
     * This magic method is executed after the object is deserialized
     * @see __sleep()
     *
     * @access public
     *
     * @return void
     */
    public function __wakeup() {
        // Turn off libxml's error logging.
        $libxmlErrors = libxml_use_internal_errors(TRUE);
        // Reload XML from string.
        $xml = @simplexml_load_string($this->asXML);
        // Reset libxml's error logging.
        libxml_use_internal_errors($libxmlErrors);
        if ($xml !== FALSE) {
            $this->asXML = '';
            $this->xml = $xml;
            // Rebuild the unserializable properties.
            $this->init();
        } else {
            Helper::devLog('Could not load XML after deserialization', DEVLOG_SEVERITY_ERROR);
        }
    }
}