How many people/viewers are online........

I'm looking for piece of code that I can place near the top of the first page of Gallery that will let me know how many ppl are online very similiar to how the nuke and mambo sites have. My gallery is separated from my main site.

The following information is required to get an answer:
Get this information from the PHP diagnostic (in the configuration wizard).
Gallery URL (optional but very useful): http://importfx.net/v1/coverage/
Gallery version: v1.5.1
Apache version: 1.3.33 (Unix)
PHP version (don't just say PHP 4, please): 4.3.11
Graphics Toolkit:
Operating system: Linux
Web browser/version (if applicable): IE & FireFox