Curl\Curl::error PHP Method

    public function error($callback)
    {
        $this->errorFunction = $callback;
    }

 /**
  * [getValidation description]
  * @param  Request $request
  * @return [type]
  */
 protected function getValidation(Request $request)
 {
     $client = $this;
     $curl = new Curl();
     $curl->success(function ($instance) use($client) {
         $client->response = new Crawler();
         $client->response->addXmlContent($instance->response);
     });
     $curl->error(function ($instance) {
         throw new CasCurlException(sprintf('Code #%s: %s', $instance->error_code, $instance->error_message));
     });
     $curl->get($this->getValidationUrl($request));
 }