public static function loadWsdlXpath($wsdlFilePath, $wsdlId)
    {
        if (!isset(self::$wsdlDomXpath[$wsdlId]) || is_null(self::$wsdlDomXpath[$wsdlId])) {
            $wsdlContent = file_get_contents($wsdlFilePath);

            if ($wsdlContent !== false) {
                self::$wsdlDomDoc[$wsdlId] = new \DOMDocument('1.0', 'UTF-8');
                self::$wsdlDomDoc[$wsdlId]->loadXML($wsdlContent);
                self::$wsdlDomXpath[$wsdlId] = new \DOMXPath(self::$wsdlDomDoc[$wsdlId]);
                self::$wsdlDomXpath[$wsdlId]->registerNamespace(
                    'wsdl',
                    'http://schemas.xmlsoap.org/wsdl/'
                );
                self::$wsdlDomXpath[$wsdlId]->registerNamespace(
                    'soap',
                    'http://schemas.xmlsoap.org/wsdl/soap/'
                );
            } else {
                throw new InvalidWsdlFileException('WSDL '.$wsdlFilePath.' could not be loaded');
            }
        }
    }