title: Paypal: Is there a way to check a cart right before a user pays?
body: <p>Is there any way currently for Paypal's API to send my site an authorization request before completing a user's payment?</p>
  
  <p>I think the answer here would be that there is no way to do this, but one can set "authorization" as a cart parameter instead of "sale". This still leaves the question of how to complete the authorization in the callback.</p>