/**
  * Returns the array of the photos in specified folder
  * @param int $folderId The identifier of the folder
  * @return array|null
  */
 public function getPhotosById($folderId)
 {
     if (!class_exists('SupsysticSlider_Photos_Model_Photos', false)) {
         if ($this->debugEnabled) {
             wp_die(sprintf('The required class \'SupsysticSlider_Photos_Model_Photos\' is does not exists in method', __METHOD__));
         }
         return null;
     }
     $photos = new SupsysticSlider_Photos_Model_Photos($this->debugEnabled);
     return $photos->getPhotosByFolderId($folderId);
 }