public function startup()
    {
        if (!$this->request->is('post') || !$this->_actionCheck()) {
            return null;
        }

        list($url) = explode('?', $this->request->getRequestTarget());

        $params = $this->_filterParams();
        if ($params) {
            $url .= '?' . http_build_query($params);
        }

        return $this->_registry->getController()->redirect($url);
    }