FormTestMachineNameForm.php

<?php

namespace Drupal\form_test\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;
use Symfony\Component\HttpFoundation\JsonResponse;

/**
 * Form constructor for testing #type 'machine_name' elements.
 *
 * @internal
 */
class FormTestMachineNameForm extends FormBase {
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'form_test_machine_name';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['machine_name_1_label'] = [
            '#type' => 'textfield',
            '#title' => 'Machine name 1 label',
        ];
        $form['machine_name_1'] = [
            '#type' => 'machine_name',
            '#title' => 'Machine name 1',
            '#description' => 'A machine name.',
            '#machine_name' => [
                'source' => [
                    'machine_name_1_label',
                ],
            ],
        ];
        $form['machine_name_2_label'] = [
            '#type' => 'textfield',
            '#title' => 'Machine name 2 label',
        ];
        $form['machine_name_2'] = [
            '#type' => 'machine_name',
            '#title' => 'Machine name 2',
            '#description' => 'Another machine name.',
            '#machine_name' => [
                'source' => [
                    'machine_name_2_label',
                ],
            ],
        ];
        $form['machine_name_3_label'] = [
            '#type' => 'textfield',
            '#title' => 'Machine name 3 label',
            '#default_value' => 'Yet another machine name',
        ];
        $form['machine_name_3'] = [
            '#type' => 'machine_name',
            '#title' => 'Machine name 3',
            '#description' => 'Another machine name.',
            '#machine_name' => [
                'source' => [
                    'machine_name_3_label',
                ],
            ],
        ];
        $form['submit'] = [
            '#type' => 'submit',
            '#value' => 'Submit',
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $form_state->setResponse(new JsonResponse($form_state->getValues()));
    }

}