DevShed continues their look at the Observer pattern in PHP with this new tutorial, part two in the series - developing a form validation system with the Observer pattern.

Well, after refreshing some of the most important points regarding the creation of observer objects, let's focus our attention on the subject of this second tutorial. Over the next few lines, I'll be demonstrating how to apply the Observer pattern during the development of a real-world application: a form validation system.

They start with the creation of the validation classes for the different data formats. They follow it with the creation of a few more, a bit more abstract classes for validation. Finally, they tie it all in, using the Observer pattern to integrate the form data inputted and the routines to check their values.