As I sit here watching “The Muppets Take Manhattan” in Spanish in the middle of a Costa Rican thunderstorm, I find my mind drifting back to a recent project where I spent a day debugging a frustratingly annoying problem: A user would visit the web application I was working on, and after a given page was loaded, all of the session data associated with their visit would be suddenly gone. The user would no longer be logged into the site, and any changes they made (which were logged in session data) were lost.

One of my favourite things about PHP 5 is how nifty the object-oriented features are. I have been able to put together surprisingly robust web applications using simple class hierarchies and abstract classes, features that only took off in PHP with the version 5.0 release. One of the other things I have loved is using the the various built-in object-oriented classes provided by the runtime, most notably the mysqli and related functionality.

One extremely common task I complete is to use database storage for session data. When you are running multiple web servers and individual HTTP requests might go to different machines, trying to come up with a scheme to synchronise session data files between the individual servers becomes prohibitive. Far better a solution is to simply put these data in the database server along with everything else (see Figure 1) – your application servers hold only the code needed to generate the pages from the database.