Warning: require_once(db.php): Failed to open stream: No such file or directory in /var/www/html/old/index.php on line 4

Fatal error: Uncaught Error: Failed opening required 'db.php' (include_path='.:/usr/share/php') in /var/www/html/old/index.php:4 Stack trace: #0 {main} thrown in /var/www/html/old/index.php on line 4