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Drupal 7: Decorate / wrap existing form as separate form with individual path

Submitted by Julian Pustkuchen on 3. July 2019 - 9:10

It's not an untypical situation: You'd like to use an existing Drupal CMS form as base for a custom form under a separate URL. In our example case we will decorate the Registration form "user_register_form" and create a separate registration form under a separate URL. This might be a custom alternative to modules like https://www.drupal.org/project/multiple_registration if they don't match your requirements.

While hook_form_alter helps to alter an existing form and will also be useful for us, we'd like to have our completely separate form with own form_id but prepopulated with the field and logic of the base form. Le'ts see how we can do this in Drupal 7:

First we'll create a separate page containing our custom form, using hook_menu() to make the form

  1. /**
  2.  * Implements hook_menu().
  3.  */
  4. function MY_MODULE_menu() {
  5.   $items['my/custom/form-path'] = array(
  6.     'title' => 'My example form decorator page',
  7.     'page callback' => 'MY_MODULE_user_register_form_wrapper_page',
  8.     'access callback' => 'user_register_access',
  9.     'type' => MENU_CALLBACK,
  10.   );
  11.   return $items;
  12. }

Next we define our form wrapper using hook_forms(). Read the API Documentation for the different methods it offers:

  1. /**
  2.  * Implements hook_forms().
  3.  */
  4. function MY_MODULE_forms($form_id, $args) {
  5.   // Wrap user register form to use it as form base for our custom form:
  6.   $forms['MY_MODULE_user_register_form'] = array(
  7.     // Use user_register_form as form base:
  8.     'callback' => 'user_register_form'
  9.   );
  10.   return $forms;
  11. }

What we do here is to "create" a custom form with form_id "MY_MODULE_user_register_form" which uses "user_register_form" as base form.

This is the form we'll call in drupal_get_form() in our page callback now to render our wrapped form instead of the user_register_form:

  1. /**
  2.  * Custom user register form page callback.
  3.  */
  4. function MY_MODULE_user_register_form_wrapper_page() {
  5.   $form = drupal_get_form('MY_MODULE_user_register_form');
  6.   return $form;
  7. }

Last but not least we alter our custom form now using hook_form_FORM_ID_alter():

  1. /**
  2.  * Implements hook_form_FORM_ID_alter().
  3.  * Decorated / wraps MY_MODULE_user_register_form.
  4.  */
  5. function MY_MODULE_form_MY_MODULE_user_register_form_alter(&$form, &$form_state, $form_id){
  6.   // Add a custom field to the wrapped form
  7.   $form['example_field'] = array(
  8.     '#type' => 'textfield',
  9.     '#title' => t('Example field'),
  10.     '#required' => TRUE,
  11.     '#weight' => 20,
  12.   );
  13.  
  14.   // Optionally add validation / submit handlers or alter them:
  15.   $form['#validate'][] = 'MY_MODULE_user_register_form_validate';
  16.   $form['#submit'][] = 'MY_MODULE_user_register_form_submit';
  17. }

That's it! Now we've created a separate registration form with form_id "MY_MODULE_user_register_form" which acts like a native Drupal form but is based on user_register_form.
Of course this kind of decorator can be used with every other Drupal form.

The final code:

  1. /**
  2.  * @file Example implementation for decorating / wrapping the user_register_form
  3.  * with a custom form on a custom page.
  4.  */
  5.  
  6. /**
  7.  * Implements hook_menu().
  8.  */
  9. function MY_MODULE_menu() {
  10.   $items['my/custom/form-path'] = array(
  11.     'title' => 'My example form decorator page',
  12.     'page callback' => 'MY_MODULE_user_register_form_wrapper_page',
  13.     'access callback' => 'user_register_access',
  14.     'type' => MENU_CALLBACK,
  15.   );
  16.   return $items;
  17. }
  18.  
  19. /**
  20.  * Implements hook_forms().
  21.  */
  22. function MY_MODULE_forms($form_id, $args) {
  23.   // Wrap user register form to use it as form base for our custom form:
  24.   $forms['MY_MODULE_user_register_form'] = array(
  25.     // Use user_register_form as form base:
  26.     'callback' => 'user_register_form'
  27.   );
  28.   return $forms;
  29. }
  30.  
  31. /**
  32.  * Implements hook_form_FORM_ID_alter().
  33.  * Decorated / wraps MY_MODULE_user_register_form.
  34.  */
  35. function MY_MODULE_form_MY_MODULE_user_register_form_alter(&$form, &$form_state, $form_id){
  36.   // Add a custom field to the wrapped form
  37.   $form['example_field'] = array(
  38.     '#type' => 'textfield',
  39.     '#title' => t('Example field'),
  40.     '#required' => TRUE,
  41.     '#weight' => 20,
  42.   );
  43.  
  44.   $form['#validate'][] = 'MY_MODULE_user_register_form_validate';
  45.   $form['#submit'][] = 'MY_MODULE_user_register_form_submit';
  46. }
  47.  
  48. /**
  49.  * Custom user register form page callback.
  50.  */
  51. function MY_MODULE_user_register_form_wrapper_page() {
  52.   $form = drupal_get_form('MY_MODULE_user_register_form');
  53.   return $form;
  54. }
  55.  
  56. /**
  57.  * Implements hook_form_validate().
  58.  * @see MY_MODULE_user_register_validate()
  59.  */
  60. function MY_MODULE_user_register_form_validate($form, &$form_state){
  61.   // Custom validation for MY_MODULE_user_register_form().
  62. }
  63.  
  64. /**
  65.  * Implements hook_form_submit().
  66.  * @see MY_MODULE_user()
  67.  */
  68. function MY_MODULE_user_register_form_submit($form, &$form_state){
  69.   // Custom submission logic for MY_MODULE_user_register_form().
  70. }

Einordnung:

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, M. Sc. WirtschaftsinformatikPhoto Julian Pustkuchen ist passionierter Software- & Webentwickler mit den Schwerpunkten Softwaredesign, Objektorientierung sowie Usability- & Ablaufoptimierung bei webks. Ein weiterer Schwerpunkt ist die Entwicklung im CMS Drupal.

Entwickelt Julian gerade keine Software, fährt er Ski, Mountainbike, spielt Badminton, segelt oder verbringt Zeit mit Freunden.

Dieser Blog dient als sein "öffentlicher Notizblo(ck/g)".

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