Is checking the value of $order->status sufficient to understand when an order has been completed?
All the checkout order statuses are prefixed with checkout_, so there is no need to check the state. Just bear in mind that in Commerce 1.x, an order may be moved into and out of that status multiple times. If you need to ensure an operation only occurs once per order, you can follow the core precedent of logging the timestamp for your operation in the $order-&gt;data array.