The Zend Framework is mainly meant for MVC use. One of the very usefull components is Zend_Form.
I have a bit trouble finding the place of Zend_Form. Is it part of t
Zend_Form does often feel like the odd man out. I think everyone's mileage varies.
Lately, most of my administrative interfaces have been very drag + drop AJAX-y, and they require a good deal of html and javascript - actual form elements are sparse. So I chose to eschew a lot of the features of Zend_Form and use it as a fancy view helper with filtering. All my validation is done on a separate layer in the model.
I think O'Phinney's idea makes a lot of sense as well. Here, he's choosing to think of the form almost as a component of the domain object - where he can add business logic. This sounds just fine, as long as you're careful to keep all the view logic for the form separated. As he notes, it's about making semantic sense. There isn't necessarily a hard and fast rule.