Gazelle/classes/file_checker.class.php

<?php
$ComicsExtensions = array_fill_keys(array('cbr', 'cbz', 'gif', 'jpeg', 'jpg', 'pdf', 'png'), true);
$MusicExtensions = array_fill_keys(
    array(
    'ac3', 'accurip', 'azw3', 'chm', 'cue', 'djv', 'djvu', 'doc', 'dts', 'epub', 'ffp',
    'flac', 'gif', 'htm', 'html', 'jpeg', 'jpg', 'lit', 'log', 'm3u', 'm3u8', 'm4a', 'm4b',
    'md5', 'mobi', 'mp3', 'mp4', 'nfo', 'pdf', 'pls', 'png', 'rtf', 'sfv', 'txt'),
    true
);
$Keywords = array(
  'ahashare.com', 'demonoid.com', 'demonoid.me', 'djtunes.com', 'h33t', 'housexclusive.net',
  'limetorrents.com', 'mixesdb.com', 'mixfiend.blogstop', 'mixtapetorrent.blogspot',
  'plixid.com', 'reggaeme.com' , 'scc.nfo', 'thepiratebay.org', 'torrentday');

function check_file($Type, $Name)
{
    check_name($Name);
    check_extensions($Type, $Name);
}

function check_name($Name)
{
    global $Keywords;
    $NameLC = strtolower($Name);
    foreach ($Keywords as &$Value) {
        if (strpos($NameLC, $Value) !== false) {
            forbidden_error($Name);
        }
    }
    if (preg_match('/INCOMPLETE~\*/i', $Name)) {
        forbidden_error($Name);
    }

    /*
     * These characters are invalid in NTFS on Windows systems:
     *    : ? / < > \ * | "
     *
     * TODO: Add "/" to the blacklist. Adding "/" to the blacklist causes problems with nested dirs, apparently.
     *
     * Only the following characters need to be escaped (see the link below):
     *    \ - ^ ]
     *
     * http://www.php.net/manual/en/regexp.reference.character-classes.php
     */
    $AllBlockedChars = ' : ? < > \ * | " ';
    if (preg_match('/[\\:?<>*|"]/', $Name, $Matches)) {
        character_error($Matches[0], $AllBlockedChars);
    }
}

function check_extensions($Type, $Name)
{
    global $MusicExtensions, $ComicsExtensions;
    if ($Type == 'Music' || $Type == 'Audiobooks' || $Type == 'Comedy' || $Type == 'E-Books') {
        if (!isset($MusicExtensions[get_file_extension($Name)])) {
            invalid_error($Name);
        }
    } elseif ($Type == 'Comics') {
        if (!isset($ComicsExtensions[get_file_extension($Name)])) {
            invalid_error($Name);
        }
    }
}

function get_file_extension($FileName)
{
    return strtolower(substr(strrchr($FileName, '.'), 1));
}

function invalid_error($Name)
{
    global $Err;
    $Err = 'The torrent contained one or more invalid files (' . display_str($Name) . ')';
}

function forbidden_error($Name)
{
    global $Err;
    $Err = 'The torrent contained one or more forbidden files (' . display_str($Name) . ')';
}

function character_error($Character, $AllBlockedChars)
{
    global $Err;
    $Err = "One or more of the files or folders in the torrent has a name that contains the forbidden character '$Character'. Please rename the files as necessary and recreate the torrent.<br /><br />\nNote: The complete list of characters that are disallowed are shown below:<br />\n\t\t$AllBlockedChars";
}