How can I modify the advanced search form when my hook runs too early?

Question

I'm using hook_form_FORM_ID_alter to modify the content of the form on the search page — I want to remove the "phrase" and "not" fields, and restrict the "only of the types" checkboxes to a hand selected list of types.

I have the following code, which is being called and which I think should work:

function MYMODULE_form_search_form_alter(&$form, &$form_state, $form_id) {
    unset($form['basic']);
    unset($form['advanced']['keywords']['phrase']);
    unset($form['advanced']['keywords']['negative']);
    unset($form['advanced']['type']);
    $form['advanced']['type'] = array(
        '#type' => 'checkboxes',
        '#title' => t('Only of the type(s)'),
        '#options' => array(
            'blog' => 'Blog entry',
            'event' => 'Event',
            'news' => 'News article'
        )
    );
    // print_r($form);
    // die;
}

Except node_form_search_form_alter gets to the search form after my form alter hook runs, so I don't get a chance to modify any of the form elements that it's adding.

I'm running Drupal 7.22.

How can I modify the advanced search form when my module hook runs before the hook that defines the advanced search form?

Answer 1

Changing the module weight will work, but sometimes that can cause problems with the order in which other hooks in your module are invoked.

Drupal provides hook_module_implements_alter() for exactly this sort of situation, so that you can target the order a specific hook is run in:

Alter the registry of modules implementing a hook.

This hook is invoked during module_implements(). A module may implement this hook in order to reorder the implementing modules, which are otherwise ordered by the module's system weight.

The code might look something like

function MYMODULE_module_implements_alter(&$implementations, $hook) {
  if ($hook == 'form_alter') {
    // Move MYMODULE to the end of the list.
    $group = $implementations['MYMODULE'];
    unset($implementations['MYMODULE']);
    $implementations['MYMODULE'] = $group;
  }
}

Once you clear the cache your module's implementation of hook_form_alter() will be invoked last (unless of course another module is implementing hook_module_implements_alter() and altering the order again. But that's a different story).

I personally prefer this method as it's just a simple code change, no need to maintain any changes to the system table in the database.

I'm not sure how well that works with a form_FORM_ID_alter hook (never tried it), but with this method you can at least make sure that only the weight for hook_form_alter() need be updated.

Actually looking at the code for drupal_alter(), changing the conditional to if ($hook == 'form_search_form_alter') would probably work.

Answer 2

Hooks are ordered by module's weight. Easiest way is to simply use Modules weight module and order them as you please:

We always need to modify modules execution order, and some could write a code that execute a query to modify the weight of a module in system table, some might go straight to his favorite SQL client and modfiy the record directly, This module provide admin interface for users/people has the access to modules page to reorder the module weights as they want, it provide a drag/drop functionality to order the contributed modules execution.

That's easy, but not portable. To make it more portable, use hook_install():

function your_module_name_install() {
  db_update('system')
    ->fields(array('weight' => your_preferred_weight))
    ->condition('name', '[your_module_name]', '=')
    ->execute();
}

or follow any other way outlined in the docs on Drupal.org.