[fw-general] Zend_Form: Adding elements to an existing display group

[Hector Virgen]

Hello,
I am having some trouble with Zend_Form and display groups (ZF 1.8.2). I
want to add an existing form element to an existing display group within the
same form, but when I call $displayGroup->addElement($element), the element
is re-added to the form, causing it to be rendered twice (once in the
display group, and again outside of the display group).

Here is my code (trimmed for clarity):

class MyForm extends Zend_Form
{
    public function init()
    {
        /* ... */
    }

    public function addStandard(Standard $standard)
    {
        $name = 'standard_' . $standard->getId();
        $this->addElement('checkbox', $name);
        $displayGroup = $this->getDisplayGroup('standards');
        $displayGroup->addElement($this->getElement($name));
    }
}

I have also tried just specifying the element's name, but that ends up in a
fatal error:

 Call to a member function getName() on a non-object in
> /usr/share/pear/Zend/Form/DisplayGroup.php on line 433


I also noticed that I cannot create a display group without adding elements
to it:

$this->addDisplayGroup(array(), 'standards'); // throws exception "No valid
elements specified for display group"

This makes it difficult to create empty display groups as containers for the
elements to be added later.

I can get around this by creating the display group automatically when the
first "standard" is added, but I am stumped on how to add the next standard
to the existing display group.

--
Hector