public function callHandler($handler_id, &$submitted, array $options)
    {
        try {
            $handlers = $this->getHandlers();
            $callback = Handler::get($handlers, $handler_id, 'validate');
            return call_user_func_array($callback, array(&$submitted, $options));
        } catch (Exception $ex) {
            return $ex->getMessage();
        }
    }