Working with Session Variables
Accessing a unique session identifier in each of your PHP documents is only the start of session functionality. When a session is started, you can store any number of variables in the $_SESSION superglobal and then access them on any session-enabled page.
If you are using a pre-4.1.x version of PHP, the $_SESSION superglobal is not present, and session functionality is much different. If you cannot upgrade to the current version of PHP, read the PHP manual section on sessions at http://www.php.net/session, which includes notes for previous releases.
Listing 10.2 adds two variables into the $_SESSION superglobal: ...