Check new form-input against old form-input

Question

I have added some extra options in the My Profile page which users can edit. But now I have to track down the change of this value...

It's a checkbox and whenever the user (un)checks this box, something must happen. So I thought this would be in the $form_state, but no luck there.

Next thing I did was to preform an EntityQuery on the user object and try to cross-reference it with the input, but again, no luck.

So how can I (programmatically) detect if a form-element goes from unchecked to checked or the other way around?

EDIT: What I try to do is an implementation with Campaign Monitor (a newsletter plugin). If a user has changed it's checkbox, his subscription must be updated (of leave it as it is when there is no change)

Answer 1

When you change something in form, that change can be found in $form_state. You need to add an AJAX callback and do your changes in that callback.

Sample code:

function MYMODULE_form_alter(&$form, $form_state, $form_id) {
  switch ($form_id) {
    case 'MY_FORM_ID':
      $form['field_select']['#ajax'] = array(
        'event' => 'change',
        'callback' => 'your_ajax_callback',
        'progress' => array('type' => 'none'),
      );
    break;
  }
}

/**
 * AJAX Callback.
 */
function your_ajax_callback(&$form, &$form_state) {
  // dpm($form_state);
  // Check $form_state here and update subscription.
}

Hope this helps!

Answer 2

I have had a similar issue and I haven't found any easy answer. My solution was to create a "consistency check" function triggered after editing content, which would compare the values provided in the form with how things are actually set-up. If the values were inconsistent with the set-up I would know that they were changed.

In other words, whenever you edit the profile set things up whether they were changed or not. In case of editing a profile it will not be too heavy for the web-page.