saving sessions

Hello, im new to the whole storing sessions thing and I really dont know how to ask this question, but here it goes. So on my site when someone logs in the login.php file checks for a the username and password in the table i created, then if it finds a match it will store a $_SESSION [] variable. To be exact the code is as follows: if ($count=='1') { session_start(); $_SESSION['user']=$user; // $user is the $_POST['user'] from the login form header('location: login_success.php'); } Now what i would like to know is how do i make my website save new changes the user made while in their account? thanks!