Using the following demonstration RPC request, the
function xmlrpc_decode_request (apparently) does not
correctly update the passed in parameter $method_name,
as described in the documentation on:
http://xmlrpc-epi.sourceforge.net/main.php?t=php_api

On a hunch, I tried changing the call to:   
  xmlrpc_decode_request($xml, &$method); 
to use call-time pass by reference. It then worked, 
but call time pass by reference is depracated:

Warning: Call-time pass-by-reference has been
deprecated - argument passed by value; If you would
like to pass it by reference, modify the declaration of
xmlrpc_decode_request(). If you would like to enable
call-time pass-by-reference, you can set
allow_call_time_pass_reference to true in your INI
file. However, future versions may not support this any
longer.

As an aside- it appears that you cannot "swallow" the warning by doing an $results = @decode( $a, &$b )... 
it stil gives the "warning, depracated" message.  So
that is possibly another bug.  I have grepped through
the source trees somewhat, but couldn't find much examples
of functions directly affecting their passed in values 
(except "sort", which is pretty complicated).

Thanks-

--Robert
(bugreport is mirrored at the sf.net pages, but that
 area appears to be mildly unmaintained)
 

<?php
$request = <<< END
<?xml version="1.0"?>
<methodCall>
<methodName>greeting</methodName>
<params>
<param>
<value><string>Dan</string></value>
</param>
</params>
</methodCall>
END;
// <?
/* ** DEBUGGING INFORMATION ** */
echo "<pre>";
echo "<b>Request:</b><br>";
print_r( $request );

// decode the request
$method_name = '';
$stuff = xmlrpc_decode_request( $request, $method_name );

echo "<b>Results:</b><br>";
print_r( $stuff );

echo "<b>Method:</b><br>";
print_r( $method_name );
echo "</pre>";
?>