If you need to use this extension but are stuck on a server where it can not be installed, the php-xmlrpc library found at http://phpxmlrpc.sourceforge.net includes an emulation layer that aims to be 100% compatible with the API of the native extension (as part of the "extras" package since version 0.2).
This means your code should be able to run unmodified on top of the php-xmlrpc library. Of course performance will be at least an order of magnitude worse...