Online PHP editor | vld for eEBeO

<?php class Calculation { } class TravelCalculation extends Calculation { } class Service { public function run(Calculation $c) { echo "Service calculation"; } } class TravelService extends Service { public function run(TravelCalculation $c) { echo "Travel Service calculation"; } } $calculation = new TravelCalculation(); $service = new TravelService(); $service->run($calculation);