FileManager.php

<?php
/**
 * FileManager.php
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * @author      André Noack <noack@data-quest.de>
 * @author      Moritz Strohm <strohm@data-quest.de>
 * @copyright   2016 Stud.IP Core-Group
 * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
 * @category    Stud.IP
 */

/**
 * The FileManager class contains methods that faciliate the management of files
 * and folders. Furthermore its methods perform necessary additional checks
 * so that files and folders are managed in a correct manner.
 *
 * It is recommended to use the methods of this class for file and folder
 * management instead of writing own methods.
 */
class FileManager
{
    //FILE HELPER METHODS

    /**
     * Removes special characters from the file name (and by that cleaning
     * the file name) so that the file name which is returned by this method
     * works on every operating system.
     *
     * @param string $file_name The file name that shall be "cleaned".
     * @param bool $shorten_name True, if the file name shall be shortened to
     *     31 characters. False, if the full length shall be kept (default).
     *
     * @return string The "cleaned" file name.
     */
    public static function cleanFileName($file_name = null, $shorten_name = false)
    {
        if(!$file_name) {
            //If you put an empty string in, you will get an empty string out!
            return $file_name;
        }

        $bad_characters = [
            ':', chr(92), '/', '"', '>', '<', '*', '|', '?',
            ' ', '(', ')', '&', '[', ']', '#', chr(36), '\'',
            '*', ';', '^', '`', '{', '}', '|', '~', chr(255)
        ];

        $replacement_characters = [
            '', '', '', '', '', '', '', '', '',
            '_', '', '', '+', '', '', '', '', '',
            '', '-', '', '', '', '', '-', '', ''
        ];

        //All control characters shall be deleted:
        for($i = 0; $i < 0x20; $i++) {
            $bad_characters[] = chr($i);
            $replacement_characters[] = '';
        }

        $clean_file_name = str_replace(
            $bad_characters,
            $replacement_characters,
            $file_name
        );