code: protected function sortByIdList($sortIds)
      {
          $fileMap = $this->foundFiles;
          if (!$fileMap) {
              return array('files' => array(), 'source' => array());
          }
          $fileKeys = array_flip(array_keys($this->uuidMap));
          $sorted   = array();
          foreach ($sortIds as $sortStringId) {
              $key          = $fileKeys[$sortStringId];
              $sorted[$key] = $fileMap[$key];
              unset($fileMap[$key]);
          }
          // Add anything not sorted yet to the end.
          $sorted += $fileMap;
  
          return $this->remapSorting($sorted, $this->outputBuffer);
      }
docs: Sort by passed id list.
  
  @param array $sortIds The list of binary ids to sort by.
  
  @return array