Sessions and Logins

Please CC me ------------- I am designing my own 'usr' class that takes care of logins. I need to know the following to finish it. ------------------------------------------------------------------- A/ Does anybody use sessions for users who are not logged into the site, and why? B/ If a user goes from unlogged in, unidentified user to a logged in, identified user, is the first session canceled and new session started? C/ (The reverse), if a user goes from logged in, identified user to a unlogged in, unidentified user, is the first session canceled and new session started? D/ How is it possible, using PHP4+ sessions, to cancel a session a page is opened with, and starting a new session? thanks all of you. I **LOVE** using this PHP 'thang' :-) Dennis