code: public function __doRequest($request, $location, $action, $version, $oneWay = null)
      {
          if (!extension_loaded('xsl')) {
              throw new Exception('PHP XSL extension is not enabled.');
          }
  
          $newRequest = $this->transformIncomingRequest($request);
  
          return parent::__doRequest($newRequest, $location, $action, $version, $oneWay);
      }
docs: __doRequest override of SoapClient
  
  @param string $request The XML SOAP request.
  @param string $location The URL to request.
  @param string $action The SOAP action.
  @param int $version The SOAP version.
  @param int|null $oneWay
  @uses parent::__doRequest
  @return string The XML SOAP response.
  @throws Exception When PHP XSL extension is not enabled or WSDL file isn't readable.