private function addBinding($serviceName)
    {
        $this->addToDebug("Adding binding: '$serviceName'");
        // SH. don't add to main doc just yet
        // $bindingTag=$this->addElement("binding");
        $bindingTag = $this->addElement('binding', $this->definitions);
        $bindingTag->setAttribute('name', $serviceName.'Binding');
        $bindingTag->setAttribute('type', 'tns:'.$serviceName.'PortType');

            //soap binding tag
            $soapBindingTag = $this->addElement('soap:binding', $bindingTag);
        $soapBindingTag->setAttribute('style', ($this->binding_style == SOAP_RPC) ? 'rpc' : 'document');
        $soapBindingTag->setAttribute('transport', 'http://schemas.xmlsoap.org/soap/http');

        //keep a reference
        $this->bindingTags[$serviceName] = $bindingTag;
        //and return
        return $bindingTag;
    }