DevShed wraps up its look at the Observer pattern in PHP with this last part of the series - centralizing the data validation of your PHP5 application using the Observer pattern.

Well, over the course of this last tutorial, I'll be moving the application of observer objects toward the real world, in this case by showing you how to include these objects within a set of form-validation classes. After reading this article, you should be equipped with a decent knowledge of how a form checking application can use the powerful features of this widely-known design pattern.

They look back first at the code for the form validation class from the previous article before moving on and building in more functionality - a FormObserver class. Finally, they pair the two classes to make a working, validating example.