passing sessions with header()

The php.net manual states: <quote> Session ID is not passed with Location header even if session.use_trans_sid is enabled. It must by passed manually using SID constant. </quote> How should the SID be passed manually? I'd like to keep the SID out of the uri, so is a POST variable the best way to handle that? My problem is that I'm trying to keep a session persistent through a header() redirect. which when left to it's own, looses all association to the session . Thanks! J