add <xml ..> to response

I'm writing wsf/php service using wsdl2php.
Can I add "<?xml version="1.0" encoding="utf-8"?>" line to the response?

--------
// create service in WSDL mode
$service = new WSService(array ("wsdl" =>"foobar.wsdl",
"actions" => $actions,
"classmap" => $class_map,
"operations" => $operations));

// process client requests and reply
$service->reply();
--------

with code above, I got a response begins with "<soapenv:Envelope>".