APNS + PHP "stream_socket_client(): Failed to enable crypto"

The sandbox push service is rate limited. I have experienced this myself when testing but have never encountered any such limit using the production API.

You might also be hitting their other protections.

Are you opening a connection, sending a message, closing connection and then looping and doing it all over again?

That will get your notifications dropped. Apple wants you to send several push notifications using the same connection, not a new one each time.

Best Practices for Managing Connections

You may establish multiple connections to the same gateway or to multiple gateway instances. If you need to send a large number of remote notifications, spread them out over connections to several different gateways. This improves performance compared to using a single connection: it lets you send the remote notifications faster, and it lets APNs deliver them faster.

Keep your connections with APNs open across multiple notifications; don’t repeatedly open and close connections. APNs treats rapid connection and disconnection as a denial-of-service attack. You should leave a connection open unless you know it will be idle for an extended period of time—for example, if you only send notifications to your users once a day it is ok to use a new connection each day.

From Apple Docs @ https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/CommunicatingWIthAPS.html

It is not necessary recreate your pem file

that error happens when you use an incorrect PassPhrase

regards Emiliano

My PHP code was generating following error:

PHP Warning:  stream_socket_client(): Failed to enable crypto in /private/tmp/t.php on line 12
PHP Warning:  stream_socket_client(): unable to connect to ssl://gateway.sandbox.push.apple.com:2195 (Unknown error) in /private/tmp/t.php on line 12
PHP Warning:  fclose() expects parameter 1 to be resource, boolean given in /private/tmp/t.php on line 24

The problem was, the damn certificate, expired the day before yesterday! :-) Can you believe this?

So, I need to recreate my PEM file.