code: protected function verifyUrl()
      {
          $UrlArray = explode("?", $this->Url);
          if (strpos($UrlArray[0], "$") !== false) {
              throw new InvalidURLException(get_called_class(), "Configured URL is ".$this->Url);
          }
          return true;
      }
docs: Verify if URL is configured properly
  @return bool
  @throws InvalidURLException