To return the response in XML-RPC format, simply omit the 'format' parameter from your request. The default response format is XML.
A simple call to the ocp.list.categories service returns this:
<?xml version="1.0" encoding="utf-8"?> <rsp stat="ok"> <object uid="1"> <field name="name">Advice, Information and Counselling</field> <field name="description"/> </object> <object uid="2"> <field name="name">Alcohol and Drug Services</field> <field name="description"/> </object> ... <object uid="32"> <field name="name">Young People</field> <field name="description"/> </object> </rsp>
If an error occurs, the following is returned:
<?xml version="1.0" encoding="utf-8"?> <rsp stat="fail"> <err code="403" msg="Error message here."/> </rsp>
You can find out more about XML-RPC at www.xmlrpc.com.