Dropdowns conditions

switch($this->data('gallery_sel')){
 case '':
   $options = {var:dropdown_search_subgallery_all};
   break;
 default:
   $options = ['N/A' => 'Please select one'];
}
return $options;

$this->set('dropdown_search_subgallery_all', $this->get('dropdown_search_subgallery_all'));