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.');
    }

}