如何在Magento中保存送货方式

Question

I am trying to save Free Shipping method with the order save by the following way:

$checkout = Mage::getSingleton('checkout/type_onepage');
$checkout->initCheckout();
$checkout->saveCheckoutMethod('register');
$checkout->saveShippingMethod('freeshipping_freeshipping');
$checkout->savePayment(array('method'=>'checkmo'));
try {
     $checkout->saveOrder();
 }
 catch (Exception $ex) {
    echo $ex->getMessage();
 }

but the shipping method is not getting saved. It's showing

No shipping information available

Even though the payment method is saved properly but the Shipping Method is not. What am I missing here ?