Fatal error: Uncaught Error: Interface 'Symfony\Component\HttpFoundation\Session\SessionBagInterface' not found in D:\xampp\htdocs\psp\backend\vendor\symfony\http-foundation\Session\Flash\FlashBagInterface.php:21 Stack trace: #0 {main} thrown in D:\xampp\htdocs\psp\backend\vendor\symfony\http-foundation\Session\Flash\FlashBagInterface.php on line 21