How do I use the subscriber option?

I started now with Pubsubhubbub (and all about realtime things), but I amhaving trouble with the Subscriber option.

I'm trying to develop a webapp in PHP to:

1. Subscribe a RSS (previously Published) to the Hub (http://pubsubhubbub.appspot.com/);
2. Read notifications (updates) from the Hub for the subscription;without succeed!!! :(

I verify that exist a library in php to the Subscriber (in Git), butusing this lib can't make the Subscribe work's (get a 409 error!).

How can I do this?