Sub forms serve several purposes:
Creating logical element groups. Since sub forms are simply forms, you can validate subforms as individual entities.
Creating multi-page forms. Since sub forms are simply forms, you can display a separate sub form per page, building up multi-page forms where each form has its own validation logic. Only once all sub forms validate would the form be considered complete.
Display groupings. Like display groups, sub forms, when rendered as part of a larger form, can be used to group elements. Be aware, however, that the master form object will have no awareness of the elements in sub forms.
A sub form may be a
Zend_Form object, or, more
Zend_Form_SubForm object. The latter
contains decorators suitable for inclusion in a larger form (i.e.,
it does not render additional HTML form tags, but does group
elements). To attach a sub form, simply add it to the form and give
it a name:
You can retrieve a sub form using either
getSubForm($name) or overloading using the sub form
// Using getSubForm():
$subForm = $form->getSubForm('subform');
// Using overloading:
$subForm = $form->subform;
Sub forms are included in form iteration, although the elements they contain are not.
Like elements and display groups, there are some operations that
might need to affect all sub forms. Unlike display groups and
elements, however, sub forms inherit most functionality from the
master form object, and the only real operation that may need to
be performed globally is setting decorators for sub forms. For
this purpose, there is the
method. In the next example, we'll set the decorator for all
subforms to be simply a fieldset (the FormElements decorator is
needed to ensure its elements are iterated):
The following methods may be used to interact with sub forms:
addSubForm(Zend_Form $form, $name, $order = null)