$zipcode_options = get_all_zipcodes_ascending();

  // Populate Ort on auktion clone.
  $selected = isset($auktion->zip_code) ? $auktion->zip_code : NULL;
  $selected = isset($form_state['values']['zip_code']) ? $form_state['values']['zip_code'] : $selected;
  $ort_options = _ajax_city_dropdown_options($selected);

  $form['zip_code'] = [
    '#type' => 'select',
    '#title' => t('PLZ'),
    '#options' => $zipcode_options,
    '#default_value' => isset($auktion->zip_code) ? $auktion->zip_code : "",
    '#select2' => ['width' => '100%', 'placeholder' => t('Enter a zipcode'), 'allowClear' => TRUE],
    '#empty_option' => '',
    '#validated' => TRUE,
    '#required' => TRUE,
    '#ajax' => array(
      'event' => 'change',
      'callback' => 'ajax_example_dependent_dropdown_callback',
      'wrapper' => 'dropdown-second-replace',
    ),
  ];

$selected = isset($auktion->zip_code) ? $auktion->zip_code : NULL;
$selected = isset($form_state['values']['zip_code']) ? $form_state['values']['zip_code'] : $selected;
$ort_options = _ajax_city_dropdown_options($selected);
if(!is_array($ort_options)){
    $ort_options=array();
}