Collapsed and collapsible Field Sets in Admin

Question

I have created a fieldset (which groups a field collection). Because it has a few nested levels and many fields, I want it to be shown collapsed. I am trying this code but it does not work. The id is retrieved directly from the source code of the web browser. The fieldset is the top-level, and there are more fieldsets inside of it. The form is displayed in the Admin page, the node edit form. The field "field-seo-general" is a #container.

function hook_form_alter(&$form, &$form_state, $form_id){
    if($form_id == "my_form"){
        $form["field-seo-general"]['options']['attributes']["#collapsible"] = TRUE;
        $form["field-seo-general"]['options']['attributes']["#collapsed"] = TRUE;
      ...
} // function

Answer 1

I have solved it installing the module Field Collection Fieldset, and instead of Embedding the Field Collection, I have put it as a Fieldset, and then one of the options is to be shown Collapsed at rendering. All with a module.

Answer 2

The field "field-seo-general" is a #container.

The The Form API entry for container does not include #collapsed or #collapsible as properties.

It seems that fieldset is the only element that can use the #collapsed and #collapsible properties.

Change the #type for field-seo-general to fieldset to make it collapsible. If field-seo-general needs to be a container, then a second option would be to create a fieldset and place the field-seo-general container within it. However, doing this will add one more dimension within the values array for your fields when the form is submitted, so you need to take that into account.

$container_seo_general = $form['field_seo_general'];
unset($form['field_seo_general']);
$fieldset = array(
  '#type' => 'fieldset',
  '#title' => 'My fieldset title',
  '#collapsible' => TRUE,
  '#collapsed' => TRUE,
);
$fieldset['field_seo_general'] = $container_seo_general;
$form['my_module_fieldset'] = $fieldset;