The Developer Tutorial website has a new article posted today about the creation of "state-enabled applications" with PHP. Basically, a chunk of functionality to keep user data persistent throughout the whole time they're on the site.

A major drawback is that while browsing from one page to another, the website does not remember the State of the browsing session. This make interactivity almost impossible. In order to increase interactivity, the developer can use the session handling features of PHP to augment the features of HTTP in order to remember the State of the browsing session.

They look at two solutions - using cookies and using sessions. Cookies are simple enough, but when it comes to sessions, there's actually two different roads to follow: with cookies enabled and without. They have to be handled slightly differently, but both essentially work the same way.