public static function getPurifier()
 {
     if (self::$purifier instanceof HTMLPurifier) {
         return self::$purifier;
     }
     require_once dirname(__FILE__) . '/../lib/vendor/htmlpurifier/library/HTMLPurifier.auto.php';
     $config = HTMLPurifier_Config::createDefault();
     $config->set('Cache.SerializerPath', sgConfiguration::get('settings.cache_dir'));
     self::$purifier = new HTMLPurifier($config);
     return self::$purifier;
 }