Fatal error: Uncaught Error: Class "PKP\db\DAO" not found in C:\xampp\htdocs\ojs\lib\pkp\classes\tombstone\DataObjectTombstoneDAO.php:23 Stack trace: #0 {main} thrown in C:\xampp\htdocs\ojs\lib\pkp\classes\tombstone\DataObjectTombstoneDAO.php on line 23