Originally posted by phpman
why? if you set the session_start() at the start of every page you can save the session anytime you want, without a iframe or hidden frame or anything.

without using the session_id for anything.
What he really wants is client-side PHP. He wants a session to be set when the user clicks a button in the browser and that can't be done directly in PHP so a hidden IFRAME is probably the next best thing.