zendframework/zf2-documentation — pull request #1196 by moderndeveloperllc (2014-02-12 18:54:16+00:00)
Title: Update zend.form.quick-start.rst - add parent::__construct() call to Factory-backed Form Extension class example

If you are extending Zend\Form\Form, you need to call the parent constructor or $this->iterator is never set and add() won't work.