Fatal error: Uncaught Error: Interface 'Symfony\Component\HttpFoundation\Session\Flash\FlashBagInterface' not found in /home/soh-works/www/websoket-sample/vendor/symfony/http-foundation/Session/Flash/FlashBag.php:19 Stack trace: #0 {main} thrown in /home/soh-works/www/websoket-sample/vendor/symfony/http-foundation/Session/Flash/FlashBag.php on line 19