Warning: require_once(config.php): Failed to open stream: No such file or directory in /volume1/web/salondewa/reservation.php on line 3

Fatal error: Uncaught Error: Failed opening required 'config.php' (include_path='.:/usr/share/pear') in /volume1/web/salondewa/reservation.php:3
Stack trace:
#0 {main}
  thrown in /volume1/web/salondewa/reservation.php on line 3