code: public function sortFiles($sortType, $sortIds = array())
      {
          switch ($sortType) {
              case 'name_desc':
                  return $this->sortByName(false);
  
              case 'date_asc':
                  return $this->sortByDate(true);
  
              case 'date_desc':
                  return $this->sortByDate(false);
  
              case 'manual':
                  return $this->sortByIdList($sortIds);
  
              case 'random':
                  return $this->sortByRandom();
  
              default:
              case 'name_asc':
          }
          return $this->sortByName(true);
      }
docs: Sorts the internal file list by a given condition.
  
  Allowed sort types are:
  name_asc  - Sort by filename ascending.
  name_desc - Sort by filename descending
  date_asc  - Sort by modification time ascending.
  date_desc - Sort by modification time descending.
  manual    - Sort by passed id array, the array must contain the binary ids of the files.
  random    - Shuffle all the files around.
  
  @param string $sortType The sort condition to be applied.
  
  @param array  $sortIds  The list of binary ids to sort by (sort type "manual" only).
  
  @return array The sorted file list.