Fatal error: Uncaught mysqli_sql_exception: Unknown database 'test_db' in C:\xampp\htdocs\test_connectMySQL.php:8 Stack trace: #0 C:\xampp\htdocs\test_connectMySQL.php(8): mysqli->__construct('localhost', 'cataloit', Object(SensitiveParameterValue), 'test_DB') #1 {main} thrown in C:\xampp\htdocs\test_connectMySQL.php on line 8