Web Database Applications with PHP and MySQL, 2nd Edition

PHP Session API and Configuration

This section describes the PHP Session Management API and Configuration parameters. We also discuss how to configure PHP to use sessions without cookies, and how PHP garbage collection removes old unused session files.

Functions for Accessing Sessions in PHP

In this section we list the key functions used to build session-based applications in PHP. By accessing session variables using the $_SESSION array, you can write complete session-based applications using just four functions:

Boolean session_start( )

Creates a new session, or finds an existing one. Checks for a session ID in the HTTP request—either as a cookie or a GET variable named PHPSESSID. If a session ID isn't included in the request, or an identified session isn't found, a new session is created. If a session ID is included in the request, and a session isn't found, a new session is created using the session ID encoded in the request. When an existing session is found, the session variables are read from the session store and initialized. Using PHP's default settings, a new session is created as a file in the /tmp directory. This function always returns true.

string session_id([string id ])

Can be used in two ways: to return the session ID of an initialized session or to set the value of a session ID before a session is created. When used to return the session ID, the function must be called without arguments after a session has been initialized. When used to set the value of the session ...