Similar to request objects, Zend_XmlRpc_Server can return custom
response objects; by default, a Zend_XmlRpc_Response_Http object
is returned, which sends an appropriate Content-Type HTTP header for
use with XML-RPC. Possible uses of a custom object would be to log
responses, or to send responses back to STDOUT.
To use a custom response class, use
Zend_XmlRpc_Server::setResponseClass() prior to calling
handle().