First off I have to say that I find this article very interesting, and have downloaded the example so I can refer to it for an upcoming project I'm going to work on.
It's been probably a year and a half since I last used PHP for web dev, but when I did, I found that there was no "standard" database independent interface, so I ended up writing my own.
I see in this example that you use MySQL specific database calls, so I'm curious to know *why*. I realize it's easiest to just write code to *one* database, but it would be much more portable to write code to a database independent interface, so that changing to a different database would be trivial. Isn't there a "standard" database independent interface (like Perl's "DBI") for PHP yet? And if there is, why didn't you use it?