Warning: require_once(./vendor/autoload.php): Failed to open stream: No such file or directory in /var/www/html/backend/index.php on line 11

Fatal error: Uncaught Error: Failed opening required './vendor/autoload.php' (include_path='.:/usr/local/lib/php') in /var/www/html/backend/index.php:11 Stack trace: #0 {main} thrown in /var/www/html/backend/index.php on line 11