hook_form_alter execution order

Question

Is there a way to change the order of execution of hook_form_alter in Drupal 7 without changing a module's weight or hacking Drupal Core?

I am trying to alter the element added in translation_form_node_form_alter from the translation module. When debugging the form I can't find the element so I assume my hook is being executed before the one in the translation module is.

Answer 1

I don't think so. translation_form_node_form_alter() implements hook_form_BASE_FORM_ID_alter() which I believe is called after hook_form_alter(), so even changing the module weight wouldn't be enough. I think your two options are to use a hook_form_BASE_FORM_ID_alter() and ensure you have a high enough module weight, or use hook_form_FORM_ID_alter() (if possible).

Answer 2

Also worth mentioning, there is a new drupal 7 API called hook_module_implements_alter() which lets you alter the execution order for a given hook WIHOUT altering the module weights table.

Sample code from the API docs showing how easy this is to do:

<?php
function hook_module_implements_alter(&$implementations, $hook) {
  if ($hook == 'rdf_mapping') {
    // Move my_module_rdf_mapping() to the end of the list. module_implements()
    // iterates through $implementations with a foreach loop which PHP iterates
    // in the order that the items were added, so to move an item to the end of
    // the array, we remove it and then add it.
    $group = $implementations['my_module'];
    unset($implementations['my_module']);
    $implementations['my_module'] = $group;
  }
}
?>

Answer 3

Here is how to make sure your hook_form_alter is called after another modules hook_form_alter:

/**
 * Implements hook_form_alter().
 */
function my_module_form_alter(&$form, &$form_state, $form_id) {
  // do your stuff
}

/**
 * Implements hook_module_implements_alter().
 *
 * Make sure that our form alter is called AFTER the same hook provided in xxx
 */
function my_module_module_implements_alter(&$implementations, $hook) {
  if ($hook == 'form_alter') {
    // Move my_module_rdf_mapping() to the end of the list. module_implements()
    // iterates through $implementations with a foreach loop which PHP iterates
    // in the order that the items were added, so to move an item to the end of
    // the array, we remove it and then add it.
    $group = $implementations['my_module'];
    unset($implementations['my_module']);
    $implementations['my_module'] = $group;
  }
}

This also works when the other module has provided a form_alter hook in the variation: hook_form_FORM_ID_alter. (they explain that in the documentation: hook_module_implements_alter).

I know that this post is quite similar to wiifm's post, but thought it useful with an example with hook_form_alter