Fatal error: Uncaught Error: Class 'Symfony\Component\HttpKernel\Event\KernelEvent' not found in D:\xampp\htdocs\psp\backend\vendor\symfony\http-kernel\Event\ControllerEvent.php:28 Stack trace: #0 {main} thrown in D:\xampp\htdocs\psp\backend\vendor\symfony\http-kernel\Event\ControllerEvent.php on line 28