Introduction to Session Management in PHP4 | Advanced PHP for Web Professionals

This chapter introduces you to session management using PHP4's built-in session management techniques.

Session management allows you to track variables associated with a user for a specific Web session. A Web session is the time that a user spends on pages on your site using the same browser instance. If the user closes the browser (or you explicitly end the session), then the session variables are no longer associated with that user, unless you provide for a way that the variables can be saved and later reassociated with the user.

Sessions are typically tracked by PHP by placing a cookie on the user's browser. The cookie references a session ID, which you can view in your scripts by calling the $PHPSESSID variable. However, using cookies is not a foolproof method to track session variables. Some users may set up their browsers so that they do not accept cookies. In these cases, your session variables cannot be tracked using the cookie method.

PHP supports link rewriting, which gets around the problems in using cookies to store session information. With link rewriting, PHP alters any links on your page so that they automatically include the $PHPSESSID variable. This does make the links look a little messy to the user, but in some cases it is the only way to be sure that you are accurately tracking a user's session.

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