Sams Teach Yourself PHP in 24 Hours, Third Edition

Starting a Session with session_start()

You need to explicitly start or resume a session unless you have changed your php.ini configuration file. By default, sessions do not start automatically. In php.ini, you will find a line containing the following:

session.auto_start = 0

By changing the value of session.auto_start to 1, you ensure that a session is initiated for every PHP document. If you don’t change this setting, you need to call the session_start() function.

PHP uses files to store session data between requests so you should also check the session.save_path directive in your php.ini file. session.save_path defines the directory on your filesystem to which session files are saved. You should ensure that it exists and that your PHP process ...