HTTP as a protocol is stateless, which doesn't make it easy for a developer. For example, your web server sends out a page to someone ordering from an online shop, and then forgets all about it. A few seconds later, the same person sends another request, ordering another item. As far as the web server is concerned, it could be an entirely different person. So to make sure the right orders are associated with the right person, a developer has to employ some sneaky tricks. Before PHP4, you could have used something like PHPLIB for session management. But PHP4 comes with a complete set of sessioning functions. This article explains how to use them.