private function addPortOperations($operation, $input = false, $output = false)
    {
        $el = $this->dom->createElement("wsdl:operation");
        $el->setAttribute('name', $operation);
        if ($input === true) {
            $input = $this->dom->createElement('wsdl:input');
            $input->setAttribute('message', $this->targetNsPrefix.":".$operation);
        }
        if ($output === true) {
            $output = $this->dom->createElement('wsdl:output');
            $output->setAttribute('message', $this->targetNsPrefix.":". $operation."Response");
        }
        $el->appendChild($input);
        $el->appendChild($output);
        
        $this->wsPortType->appendChild($el);
    }