Alternative to $_SERVER['DOCUMENT_ROOT']?

From: D. Alvarado (laredotornado_at_zipmail.com)
Date: 09/21/04 

Date: 21 Sep 2004 14:04:58 -0700

Hello, I am running PHP 4 on my Fedora Core 2 dev machine. I made a
lot of calls to $_SERVER['DOCUMENT_ROOT']. Unfortunately, when I move
my application to a Windows environment, running on an IIS web server,
the variable $_SERVER['DOCUMENT_ROOT'] is no longer supported (I
always get an empty string). Is there another variable I should query
that would return this information? I am at the mercy of the hosting
company so sadly, it is probably unlikely that they'll add
'DOCUMENT_ROOT' into their environment variable configuration.

Thanks for your help, - Dave