I am running magento ver. in my site.

I want to customize shipping rate when a particular coupon is applied.

How can I do that when "Apply Coupon" button is clicked, if a given coupon is the one, that is applied ?

I never had much encounter with code in price rule section so I am not aware of which controller is executed when "Apply Coupon"(Cart price rule) is clicked.

1 Answer 1


If you check the HTML of the form you'll see it posts to http://domain.com/checkout/cart/couponPost/.

Magento works with a router that breaks down the URL in [module]/[controller]/[action] which means you know the class and method that handles the post: Mage_Checkout_CartController::couponPostAction.

Now please don't fire up your editor and put the code in that method. The method actually adds the coupon code to the quote and calls collectTotals in class Mage_Sales_Model_Quote which in turn calls _validateCouponCode on line 1376.

I would suggest running your code after that so you're sure the code was valid and applied.

On line 1378 the event sales_quote_collect_totals_after is called. I would use that event to do your magic. The next steps would be:

Which would look like something below.




class [Module]_[Namespace]_Model_Observer
       $quote = $observer->getQuote();
       $couponcode = $quote->getData('coupon_code');
       if ($couponcode == '[your coupon code]') {
           * Your custom code here

       return $this;

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