Ripcord is an PHP 5 XML-RPC server and client library with a very simple and easy to use API. You can create XML-RPC, (simplified) SOAP 1.1, and SimpleRPC clients with one call and then call RPC methods as if they were local methods of the client. You can create a server with one call, passing it any number of objects or classes whose methods it will publish and automatically document.
XRDL is a language and tools for automatic client generation for XML-RPC services. It provides a way to create simple service definitions for XML-RPC services. It is inspired by WSDL, but aims for ease of use in the spirit of XML-RPC. It supports exporting complex (recursive) types, as well as methods. It includes a number of tools, allowing automatic XRDL generation for servers and clients written in PHP or C++/Qt.