|  |  | 
 |  |  |       return $bestOffset; | 
 |  |  |    } | 
 |  |  |     | 
 |  |  |    public function mapUsingOffset($offset) { | 
 |  |  |    public function mapUsingOffset($offset, $mapper) { | 
 |  |  |       $result = []; | 
 |  |  |       foreach($this->gtfsrtTrips as $gtfsTripId => $gtfsTrip) { | 
 |  |  |          $ttssTripId = $gtfsTripId + $offset; | 
 |  |  |          if(isset($this->ttssTrips[$ttssTripId])) { | 
 |  |  |             $data = numToTypeB($gtfsTrip['id']); | 
 |  |  |             $data = $mapper($gtfsTrip['id']); | 
 |  |  |             $num = $gtfsTrip['num']; | 
 |  |  |             if(!is_array($data) || !isset($data['num'])) { | 
 |  |  |                $data = [ | 
 |  |  |                   'num' => $num, | 
 |  |  |                   'low' => 2, | 
 |  |  |                   'num' => $num ?: '??'.$gtfsTrip['id'], | 
 |  |  |                   'low' => NULL, | 
 |  |  |                ]; | 
 |  |  |             } elseif($data['num'] != $num) { | 
 |  |  |                // Ignore due to incorrect depot markings in the data |