mwillbanks/Zend_Mobile — pull request #15 by JochenHeizmann (2012-07-06 14:58:35+00:00)
Title: Field "collapse_key" must be a JSON String

If you enter a numeric id, you will get a Zend_Mobile_Push_Exception_InvalidPayload-Exception with the response:

"Field "collapse_key" must be a JSON String".