XML-RPC is a "...remote procedure calling using HTTP as the transport and XML as the encoding. XML-RPC is designed to be as simple as possible, while allowing complex data structures to be transmitted, processed and returned." (XML-RPC Home Page).

The Zend Framework implementation for XML-RPC clients (and in the future for XML-RPC servers) makes the usage of XML-RPC even simpler, by trying to make XML-RPC usage as similar as possible to the PHP5 SOAP web service extension.