FormTestGetForm.php

<?php

namespace Drupal\form_test\Form;

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

/**
 * Form to test whether GET forms have a CSRF token.
 *
 * @internal
 */
class FormTestGetForm extends FormBase {
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'form_test_get_form';
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $form['#method'] = 'get';
    $form['submit'] = [
      '#type' => 'submit',
      '#value' => 'Save',
    ];
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $this->messenger()
      ->addStatus('The form_test_get_form form has been submitted successfully.');
  }

}