code: public function addPingback($url)
      {
          $response = $this
              ->getHttpClient()
              ->request('GET', "/res.php?key={$this->apiKey}&action=add_pingback&addr={$url}");
  
          $responseText = $response->getBody()->__toString();
  
          if ($responseText === self::STATUS_OK) {
              return true;
          }
  
          throw new ErrorResponseException(
              $this->getErrorMessage($responseText) ?: $responseText,
              $this->getErrorCode($responseText) ?: 0
          );
      }
docs: Add pingback url to rucaptcha whitelist.
  
  @param string $url
  @return bool                     # true if added and exception if fail
  @throws ErrorResponseException
  @throws \GuzzleHttp\Exception\GuzzleException