how to read an xml document from a web method parameter in a php soap server

[mike]

hi,
i'm sure (i hope!) there's a simple way of doing this, so even a url to
example would be fine...

i have a wsdl generated by .net
i use this wsdl to implement a webservice in php
i have a web method like action(XmlDocument doc)
from a .net client i want to do something like soap.action(doc)

on the php side i have something like
function action($parameter)
{
$doc = $parameter->doc;
}

the class for $parameter is fully defined with the same name as that
defined in the wsdl, however...

both $parameter and $doc have class "std class", which means i cannot
process/save $doc as a DOMDocument.

i've also tried $classmap without success.

i'm new to php so any suggestions gratefully received.

many thanks,
mike.