Matthew Weier O'Phinney, Zend Framework guru, has posted the simplest Zend_Form decorator hw could come up with:

I've been seeing ranting and general confusion about Zend_Form decorators (as well as the occasional praises), and thought I'd do a mini-series of blog posts showing how they work.

He creates a sample object set to illustrate what the Decorator pattern is - a LockedWindow and StandardWindow that implement a Window interface, a Person object and, as applied to a Zend_Form instance, a My_Decorator_SimpleInput decorator that adds in a new type of input field. The decorator is applied through the configuration array for the Zend_Form_Element in a "decorators" array item.