xmlrpc_encode_request does not produce XML output

This is perhaps before beginner question:
function:
xmlrpc_encode_request('method1','param1')
produces output:
method1 param1
expected:
xml formatted request string
question:
is there something missing in my installation or am I doing something wrong
? (tried Apache 1.3.31 on Linux and Windows - the same output). thank you
for help.