class RecursivePlaceholdersTest

class RecursivePlaceholdersTest implements TrustedCallbackInterface {
  
  /**
   * #lazy_builder callback; bubbles another placeholder.
   *
   * @param string $animal
   *   An animal.
   *
   * @return array
   *   A renderable array.
   */
  public static function callback($animal) {
    return [
      'another' => [
        '#create_placeholder' => TRUE,
        '#lazy_builder' => [
          'Drupal\\Tests\\Core\\Render\\PlaceholdersTest::callback',
          [
            $animal,
          ],
        ],
      ],
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public static function trustedCallbacks() {
    return [
      'callback',
    ];
  }

}