Warning: require(/var/www/app/vendor/autoload.php): Failed to open stream: No such file or directory in /var/www/app/index.php on line 16

Fatal error: Uncaught Error: Failed opening required '/var/www/app/vendor/autoload.php' (include_path='.:/usr/local/lib/php') in /var/www/app/index.php:16 Stack trace: #0 {main} thrown in /var/www/app/index.php on line 16