To debug a SOAP service using SoapServer(), a WSDL file and Zend Studio Client/Server, you have to append ?start_debug=1&debug_port=10000 to the service location:
--- snip ---
... method / service definition ....
<service name="SOAPService">
<port
name="SOAPServicePort"
binding="typens:SOAPServiceBinding">
<soap:address
location="$URL?start_debug=1&debug_port=10000"/>
</port>
</service>
--- snap ---