How do i programatically reset the values of an AJAX submitted form for Drupal 8? I Want to reset them with an AJAX callback. Here is my current callback. It works because i'm forcing the values to NULL.

      public function resetFormCallback(array &$form, FormStateInterface $form_state) {


          $form['address']['#value']    = NULL;
          $form['customer']['#value']   = NULL;
          $form['name']['#value']       = NULL;
          $form['email']['#value']      = NULL;
          $form['location']['#value']   = NULL;
          $form['zip_code_1']['#value'] = NULL;
          $form['zip_code_2']['#value'] = NULL;
          $form['phone']['#value']      = NULL;
          $form['subject']['#value']    = NULL;
          $form['message']['#value']    = NULL;

          return $form;
  • $form_state->setUserInput([]); $form_state->setRebuild();
    – user21641
    Commented Jul 12, 2017 at 17:33
  • That doesn't cleans my input values. Do notice i do return $form at the end of my callback. Commented Jul 12, 2017 at 17:36

1 Answer 1


I found a couple solutions that works in Drupal 9 that should also work in 8. Untested.

In my buildForm() I am setting some '#default_valueswith$form_state->getValue('name')`. Maybe you are too?

In my case I have a non ajax version of the form that does not have a clear button. In my ajax form's buildForm() function; I simply add "unset()" to the beginning of the form because there is never an instance in which the form needs to be pre-populated on page load in my case. The form will not reload in-between state changes either, so we never have to worry about `#default_value' being set.


public function buildForm(array $form, FormStateInterface $form_state) {
    //get parent's form
    $form = parent::buildForm($form, $form_state);
    //unset default values so the form clears properly
    // the rest of your form modifications

    return $form

Alternatively or in addition to, if you need your form to be pre-populated on page load via arguments (might be overkill); In your ajax buildForm() you can detect the last callback made and preform your unsets within:

//within the buildForm() ajax function, example clear button with your callback name
$form['clear'] = [
      '#type' => 'button',
      '#value' => $this->t('Clear'),
      '#ajax' => [
        'callback' => '::resetFormCallback',
        'event' => 'click',

//Check the operating button that submitted a callback action that rebuilt the form
//assign boolean
$form_cleared = 'Clear' === (string) $form_state->getValue('op');
if($form_cleared) {
  //preform unsets here

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