code: public function getPingbacks()
      {
          $response = $this
              ->getHttpClient()
              ->request('GET', "/res.php?key={$this->apiKey}&action=get_pingback");
  
          $responseText = $response->getBody()->__toString();
  
          if (strpos($responseText, 'OK|') !== false) {
              $data = explode('|', $responseText);
              unset($data[0]);
              return empty($data[1]) ? [] : array_values($data);
          }
  
          throw new ErrorResponseException(
              $this->getErrorMessage($responseText) ?: $responseText,
              $this->getErrorCode($responseText) ?: 0
          );
      }
docs: Returns pingback whitelist items.
  
  @return string[]                 # List of urls
  @throws ErrorResponseException
  @throws \GuzzleHttp\Exception\GuzzleException