We found a little bug in the implementation of the system.multicall() functionality of the class "Zend_XmlRpc_Server_System".

As you can see on http://replay.web.archive.org/20060824100531/… every response of a multicall should be packed inside a one-element array: "Notice that regular return values are always nested inside a one-element array. This allows you to return structs from functions without confusing them with faults."

In the Zend/XmlRpc/Server/System.php file on line 145 (ZF version 1.11.5) is this line: "$responses[] = $response->getReturnValue();"

This snippet would add the return value of a xmlrpc-method as plaintext to the responses-array like this example, not as a one-element array, as the client would expect.

So the only thing, we have to change is this line to the following: "$responses[] = array($response->getReturnValue());"