New from Developer.com today, there's this article dealing with the improvements in the object-oriented functionality of PHP5 and its ability to easily create abstract classes - in this case, a database abstraction layer.
PHP 5 made significant improvements on the Object Orientated programming model of PHP 4 bringing it more in line with languages such as Visual Basic .NET and Java. The improved object model in PHP 5 makes developing applications using OOP much easier and gives you the programmer, greater flexibility.
In this series of articles I will demonstrate the new features of the PHP 5 object and show you how to create a database abstraction layer similar to PEAR DB. I will also introduce you to a few design patterns that can be applied to common OOP related problems.
They introduce a bit about abstraction in PHP5, including examples of abstract classes and how they can be extended easily. With this basic knowledge shared, they show a list of functions they're going to implement in the database layer, making defining them a requirement in any "child" classes. For now, their interface just links the custom function calls back to the normal MySQL functionality in PHP, but will be extended later.