Change PHP fom amazon FPS from credit card payment to credit card authorization and no payment

On [this][1] website, when you click sign up, it takes you to make a payment with amazon. I want to change it from making a payment to just making a reserve or authorization, that I can convert to a payment later. See [login to view URL] for an example of this. Page 26 of the api <[login to view URL]> talks about what the difference between 'pay' and 'reserve' is. Just need someone to update my php code to the reserve option.