FormTestCheckboxesZeroForm.php

<?php

namespace Drupal\form_test\Form;

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

/**
 * Tests checkboxes zero.
 *
 * @internal
 */
class FormTestCheckboxesZeroForm extends FormBase {
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'form_test_checkboxes_zero';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state, $json = TRUE) {
        $form_state->set('json', $json);
        $form['checkbox_off'] = [
            '#title' => t('Checkbox off'),
            '#type' => 'checkboxes',
            '#options' => [
                'foo',
                'bar',
                'baz',
            ],
        ];
        $form['checkbox_zero_default'] = [
            '#title' => t('Zero default'),
            '#type' => 'checkboxes',
            '#options' => [
                'foo',
                'bar',
                'baz',
            ],
            '#default_value' => [
                0,
            ],
        ];
        $form['checkbox_string_zero_default'] = [
            '#title' => t('Zero default (string)'),
            '#type' => 'checkboxes',
            '#options' => [
                'foo',
                'bar',
                'baz',
            ],
            '#default_value' => [
                '0',
            ],
        ];
        $form['submit'] = [
            '#type' => 'submit',
            '#value' => 'Save',
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        if ($form_state->get('json')) {
            $form_state->setResponse(new JsonResponse($form_state->getValues()));
        }
        else {
            $form_state->disableRedirect();
        }
    }

}