On PHPBuilder.com there's a new tutorial posted showing you how to create a user authentication system that uses sessions to handle the logged in user's information.

Outside of installation and configuration issues, reader questions pertaining to user authentication and session management almost certainly rank among the most common I receive on an ongoing basis. The logic itself is pretty straightforward; however, even a simple implementation involves a number of small but important details which aren't always so easy to figure out the first time around. This tutorial serves to dispel much of the confusion by guiding you through the implementation of a simple user authentication feature which will subsequently keep the user logged in via a session.

He helps you create the simple login form, a table in MySQL to store the user data in and the PHP script (complete with input filtering) to handle the login. The system also tracks the last login of each user by updating the table with a timestamp each time they successfully log in.