public function isValid($value)
    {
        if (!$value) {
            $this->error(self::MISSING_VALUE);
            return false;
        }

        $response = $this->getService()->verify($value);

        if ($response->getStatus() === true) {
            return true;
        }

        $this->error(self::ERR_CAPTCHA);
        return false;
    }