Fatal error: Uncaught Error: Undefined constant "PKP\services\PKP_STRICT_MODE" in C:\xampp\htdocs\ojs\lib\pkp\classes\services\PKPSchemaService.php:615 Stack trace: #0 {main} thrown in C:\xampp\htdocs\ojs\lib\pkp\classes\services\PKPSchemaService.php on line 615