Fatal error: Uncaught Error: Undefined constant "Database\DB_HOST" in /var/www/html/lib/Database/Connection.php:60 Stack trace: #0 /var/www/html/lib/Model/Base/Basemodel.php(74): Database\Connection::getInstance() #1 /var/www/html/grepper_api/view_product.php(10): Model\Base\Basemodel->fetchRow('16') #2 {main} thrown in /var/www/html/lib/Database/Connection.php on line 60