Once I needed to make some XML-RPC method calls, but faced with the lack of simple implementation of it.
I tried to use different libraries, but they are too complicated. For, example PEAR's xml-rpc implementation is quite difficult to install on Windows and not always possible to install on Linux shared hosting. And XML-RPC for PHP at sourceforge have some problems with UTF-8 characters encoding. So I created my on simple XML-RPC client.