The downloads and the online guide should help you get started. I use MSSQLServer and had no issues following the connection guides on the getting-started section.

https://www.gridphp.com/docs/

If you check the Demos\loading folder, there is a PDO file that demonstrates connecting with PDO.

$db_conf = array();
$db_conf["type"] = "pdo";
$db_conf["server"] = "mysql:host=localhost;port=3306";
$db_conf["user"] = PHPGRID_DBUSER; // username
$db_conf["password"] = PHPGRID_DBPASS; // password
$db_conf["database"] = PHPGRID_DBNAME; // database