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Reserved methods

Table of Contents

In order to extend the functionality offered by XML-RPC servers without impacting on the protocol, I've included experimental support in this release for reserved methods.

All methods starting with system. are considered reserved by the server. PHP for XML-RPC itself provides three special methods, detailed in this chapter.


This method may be used to enumerate the methods implemented by the XML-RPC server.

The system.listMethods method requires no parameters. It returns an array of strings, each of which is the name of a method implemented by the server.


This method takes one parameter, the name of a method implemented by the XML-RPC server.

It returns an array of possible signatures for this method. A signature is an array of types. The first of these types is the return type of the method, the rest are parameters.

Multiple signatures (ie. overloading) are permitted: this is the reason that an array of signatures are returned by this method.

Signatures themselves are restricted to the top level parameters expected by a method. For instance if a method expects one array of structs as a parameter, and it returns a string, its signature is simply "string, array". If it expects three integers, its signature is "string, int, int, int".

If no signature is defined for the method, a none-array value is returned. Therefore this is the way to test for a non-signature, if $resp below is the response object from a method call to system.methodSignature:

if ($v->kindOf()!="array") {
  // then the method did not have a signature defined

See the introspect.php demo included in this distribution for an example of using this method.


This method takes one parameter, the name of a method implemented by the XML-RPC server.

It returns a documentation string describing the use of that method. If no such string is available, an empty string is returned.

The documentation string may contain HTML markup.