ZF-2562: Create interfaces for the various Zend_Form classes


Currently, Zend_Form has only concrete classes. For issues of composition and extendibility, we should have one or more interfaces which can be used to create alternate implementations.


Base interface covering shared functionality of all class types

Form interface

Display Group Interface

Element interface

SubForm interface

The interfaces became too bloated and complex to be usable. While there were a finite number of methods required for each, there were also issues with multiple interfaces interfering with each other (e.g., Iterator, Zend_Form_Interface), and the fact that Zend_Form itself implemented all but the Element and DisplayGroup interfaces in order to keep the current API.

Closing as "Won't Fix".