How to add custom field to order in Magento?

Question

I want to add one new custom field to one page checkout in Magento. I have created a module with installer:

$installer = $this;
$installer->startSetup();
$set         


        

Answer 1

Add an observer :

    
        
            
                singleton
                mymodule/observer
                Savefield
            
        
    

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);
    }   
}