DevShed has posted a tutorial that talkes about a simple way to keep track of user information (or any other info) as a user navigates your site - using PHP sessions.
In PHP, session management is used to help web applications maintain their state across several HTTP requests when needed. In this first part of a series, you will learn the basics of the PHP built-in session mechanism, as well as some of its many useful functions.
Since PHP sessions are one of those things that sooner or later you must learn as a PHP developer, in this article I shall provide an overview of them. I will begin with the basics of how to use them, highlighting their strong points and weaknesses, and finally explore some of their most advanced concepts. By the end of this series, you should have all the knowledge that you need to start using the most common PHP session management functions, so you can use them during the development of your own applications.
They explain the basics of sessions and how they can be used in your apps, how to destroy a session, some of the variou ssession functions, and how you can configure your sessions and session hander to fit your needs.