FormTestSubmitButtonAttributeForm.php

<?php

declare (strict_types=1);
namespace Drupal\form_test\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;

/**
 * Builds a simple form to test the submit_button attribute.
 *
 * @internal
 */
class FormTestSubmitButtonAttributeForm extends FormBase {
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() : string {
    return 'form_test_submit_button_attribute';
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state, $customize = FALSE) : array {
    $form['submit-button-attr'] = [
      '#type' => 'button',
      '#submit_button' => TRUE,
      '#value' => $this->t('Try to Submit'),
    ];
    if ($customize) {
      $form['submit-button-attr'] = [
        '#type' => 'button',
        '#submit_button' => FALSE,
        '#value' => $this->t('Submit if you can'),
      ];
    }
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) : void {
  }

}