calling static class functions using a function variable

Hi all, Hope you can help. I have an class called xml and a class method called hi_handler. I am able to call this method statically as follows: xml::hi_handler($attrs); but when I try to call it like this, it fails miserably: $junk="xml::hi_handler"; $junk(); Fatal error: Call to undefined function: xml::hi_handler() Any ideas - besides the obvious way of using a dummy instance. I am using php 4.0.3pl1 Thanks, Shaun --