hook_form_alter

Perform alterations before a form is rendered.

One popular use of this hook is to add form elements to the node form. When altering a node form, the node object can be accessed at $form['#node'].

In addition to hook_form_alter(), which is called for all forms, there are two more specific form hooks available. The first, hook_form_BASE_FORM_ID_alter(), allows targeting of a form/forms via a base form (if one exists). The second, hook_form_FORM_ID_alter(), can be used to target a specific form directly.

The call order is as follows: all existing form alter functions are called for module A, then all for module B, etc., followed by all for any base theme(s), and finally for the theme itself. The module order is determined by system weight, then by module name.

Within each module, form alter hooks are called in the following order: first, hook_form_alter(); second, hook_form_BASE_FORM_ID_alter(); third, hook_form_FORM_ID_alter(). So, for each module, the more general hooks are called first followed by the more specific.

Parameters

$form: Nested array of form elements that comprise the form.

$form_state: A keyed array containing the current state of the form. The arguments that drupal_get_form() was originally called with are available in the array $form_state['build_info']['args'].

$form_id: String representing the name of the form itself. Typically this is the name of the function that generated the form.

See also

hook_form_BASE_FORM_ID_alter()

hook_form_FORM_ID_alter()

Related topics

Hooks

Allow modules to interact with the Drupal core.

42 functions implement hook_form_alter()

File

modules/system/system.api.php, line 1616

Hooks provided by Drupal core and the System module.

Code

function hook_form_alter(&$form, &$form_state, $form_id) {
  if (isset($form['type']) && $form['type']['#value'] . '_node_settings' == $form_id) {
    $form['workflow']['upload_' . $form['type']['#value']] = array(
      '#type' => 'radios', 
      '#title' => t('Attachments'), 
      '#default_value' => variable_get('upload_' . $form['type']['#value'], 1), 
      '#options' => array(t('Disabled'), t('Enabled')),
    );
  }
}