private function _verifyResponse($recaptchaResponse)
    {
        $data = http_build_query(array(
                'secret' => $this->_params->get('secret-key'),
                'response' => $recaptchaResponse
            )
        );

        $options = array('http' => array(
                'method'  => 'POST',
                'header'  => 'Content-type: application/x-www-form-urlencoded',
                'content' => $data
            )
        );

        $context = stream_context_create($options);
        $response = file_get_contents('https://www.google.com/recaptcha/api/siteverify', false, $context);
        $result = json_decode($response);

        return (bool) $result->success;
    }