Is is possible to set a default PDO fetch mode?

$connection = new PDO($connection_string);
$connection->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ);

$dsn = 'mysql:host='.$db_server.';dbname='.$db_name.';port='.$db_port;
$driver_options = array(
   PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8'",
   PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
   PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_OBJ,
);               
$dbh = new PDO( $dsn, $db_user, $db_pass, $driver_options );