Table of Contents
In order to extend the functionality offered by XML-RPC servers without impacting on the protocol, reserved methods are supported in this release.
All methods starting with system. are
    considered reserved by the server. PHP for XML-RPC itself provides four
    special methods, detailed in this chapter.
Note that all server objects will automatically respond to clients
    querying these methods, unless the property
    allow_system_funcs has been set to
    false before calling the
    service() method. This might pose a security risk
    if the server is exposed to public access, e.g. on the internet.