public static function fields($orderId, $orderAmount, $orderName = null, $orderDesc = null)
	{

		$fields = self::gateway()->endpoint(array(
			'orderId'     => $orderId,
			'orderAmount' => $orderAmount,
			'orderName'   => $orderName,
			'orderDesc'   => $orderDesc,
		));

		foreach ($fields as $key => $val) {
			echo '<input
				type="hidden"
				name="' . htmlentities($key) . '"
				value="' . htmlentities($val) . '">
			';
		}

	}