?xsd is an standard option to serve an xsd file imported within a wsdl. This was a missing feature in WSF/PHP. In WSF/PHP automatic wsdl generation, it does not generate additional xsds which are imported by the wsdl and hence this option would not be required. However, with wsdl mode, you could have additional xsds imported in the wsdl. Now you can obtain these xsds with the option ?xsd=xsdfilename.xsd.