I am wondering, is there any way to add a custom fieldset to an admin form, without overwriting Form container class of that admin-form.

I will explain it little bit. Suppose we need to add a new fieldset in CMS_Block. We can achieve this by rewrite _preapreForm() method of class Mage_Adminhtml_Block_Cms_Block_Edit_Form. Here we need to do somewhat this in order to achieve our goal

class Namespace_Modulename_Block_Adminhtml_Cms_Block_Edit_Form extends Mage_Adminhtml_Block_Cms_Block_Edit_Form{
    protected function _prepareForm()

           add new fieldset and fields here

However I don't like to do rewrite of a core class (Since Its not a good practice). Is there any other approach exist to achieve the same result. I just want to add a new field sets with a custom module on an admin form with two conditions

  1. Without touching core files

  2. Without doing rewrite

  • What is about layout update? Or using event for specific controller/action render?
    – Amasty
    Commented Aug 13, 2014 at 10:27
  • @Amasty layout update wont work. Please review the answer that marius made Commented Aug 13, 2014 at 10:28

1 Answer 1


You can try to observe the event adminhtml_block_html_before.
but that gets dispatched for every block that is a child of Mage_Adminhtml_Block_Template.
So you will need to to a check first to see if the block matches your need.
something like this:

public function addFields($observer) {
    $block = $observer->getEvent()->getBlock();
    if ($block instanceof Mage_Adminhtml_Block_Cms_Block_Edit_Form) {
         //do your magic here
  • observers are better than rewrite. But still its not a clean method. Coz almost every admin blocks are child of Mage_Admin_Html_Template. Is there any way to achieve this through layout ? But when I deeply thinking about it, it gave me a feeling that, my block would include outside of the form. @marius Commented Aug 13, 2014 at 10:24
  • @programmer_rkt I don't think there is a way to do it through layout files. The block in question does not appear in the layout files. It is instantiated via the parent block.
    – Marius
    Commented Aug 13, 2014 at 10:26
  • and secondly I have a friendly question to you. Which method you normally adopt to do this job? Commented Aug 13, 2014 at 10:26
  • So as per your suggestion, there is probably these two ways exist to do this right ? Commented Aug 13, 2014 at 10:29
  • i suggest that this as event every time for admin block,if you add controller full action name as ccondtion then it it be better.....$action = Mage::app()->getFrontController()->getAction(); $action->getFullActionName() if($action->getFullActionName()='adminhtml_cms_block_edit){ // marius code }
    – Amit Bera
    Commented Aug 13, 2014 at 10:30

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