using <?=SID?> inside a function?

Hello all, I'm building some session management routines, and I only want to pass the session id in the URL when the user is not accepting cookies - I like to keep my URL's clean if possible, so I don't want to just use &gt;?=SID?%lt; willy nilly, by enabling trans-sid. I have a function that writes my links, which will add the session variable using ?PHPSESSID=$PHPSESSID, but that won't work on the same page that calls the session.start(). Here's how it works so far, when the user first hits the site, I set the cookie with session.start() and register a session variable called $use_sid boolean. I then send the cookie and the URL parameter. Subsequent pages check for the existence of $HTTP_COOKIE_VARS["PHPSESSID"] and turns $use_sid on or off as necessary. I use a functions to write all of my html, including links, so it's easy for $use_sid to add the session id to all urls on the page when necessary. Here's my problem - on the page that starts the session, the url rewrite function adds the ?PHPSESSID= but not it's value. On the same test page, using &gt;?=SID?%lt; works fine. I can only assume that the &gt;?=SID?%lt; rewrite happens after the page code is written. Can anyone suggest a work around to make that value available, or provide syntax for using SID within a function. I have only seen it written as &gt;?=SID?%lt; which won't work for my use. Any suggestions - no example I've encountered treats the session id this way. Thanks, J!M