添加观察者:

<events>
    <checkout_type_onepage_save_order>
        <observers>
            <Savefield_observer>
                <type>singleton</type>
                <class>mymodule/observer</class>
                <method>Savefield</method>
            </Savefield_observer>
        </observers>
    </checkout_type_onepage_save_order>
</events>

然后在 mymodule/savefield/model/obsever.php 文件中添加以下内容:

And in the mymodule/savefield/model/obsever.php file add this:

class Mymodule_Savefield_Model_Observer
{
    public function Savefield($observer){
        //get event data
        $event = $observer->getEvent();

        //get order
        $order = $event->getOrder();

        //set the variable here
        $order->setMyField($fieldVal);
    }   
}