code: public static function exaluateXpathQueryOnWsdl($wsdlId, $wsdlFilePath, $xpath)
      {
          WsdlAnalyser::loadWsdlXpath($wsdlFilePath, $wsdlId);
  
          return self::$wsdlDomXpath[$wsdlId]->evaluate($xpath);
      }
docs: Evaluate an XPATH query on a given WSDL
  
  @param string $wsdlId
  @param string $wsdlFilePath
  @param string $xpath XPATH query
  @return string|null