ORIG_SCRIPT_NAME

I have PHP 5.0.2 working in Apache 2.0.52 as a module, on WinXP SP2, and I'm trying to test coWiki (CVS-HEAD). I'm using Komodo 3.0.1 (eval) to debug it over the XDebug 2.0 beta1 debugger. There is a point in the code which fails because $_SERVER['ORIG_SERVER_NAME'] is not defined. As a matter of fact, phpinfo() show none of the ORIG_ variables are defined. Is there a php.ini configuration option which might affect this, or is this a function of mod_php vs. CGI execution? Kevin (newbie - be gentle) ;)