zendframework/zf1 — pull request #459 by ShishkinAR (2014-11-14 08:25:20+00:00)
Title: Sending APNS without sound

If I want to send APNS without sound - it should be without option "sound" in a dictionary.
See https://developer.apple.com/library/mac/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/ApplePushService.html, Table 3-1.