php - Magento after Onepage checkout adding new products to cart -

I want to add some products after checkout, I have a supervisor and are listening on 'checkout_onepage_controller_success_action'

When I try

$ this -> _ getcart () -> addProduct ($ product, $ parameter);

And to save the car, the success page will load, but no new product in the cart.

Any ideas what is wrong?

This is working if you

$ cart = mage :: getSingleton ('Checkout / Cart');

Before you do a