The Googlebot and Sessionid's

[LanciaStratos]

Dontom posted the following code over at vB.com, and I want to use it on my forums to set the sessionid to null when the http-user-agent is the Googlebot, so Google won't have any trouble crawling my forum pages.

PHP Code:

if (eregi("googlebot",getenv("HTTP_USER_AGENT" )) || eregi("internetseer",getenv("HTTP_USER_AGENT" )) || eregi("WebCrawler",getenv("HTTP_USER_AGENT" ))) { 
$session = NULL;
} 


Now, before I go off adding this to my forum, my question is, will this code actually do the job, and where should I insert this code to get the job done?