How to create a SSL connection in PHP with SO_KEEPALIVE?

Question

I have some simple PHP code that creates a SSL connection

$streamContext = stream_context_create();
stream_context_set_option($streamContext, 'ssl', 'local_cert', $this->sslPem);
stream_context_set_option($streamContext, 'ssl', 'passphrase', $this->passPhrase);

$this->apnsConnection = stream_socket_client('ssl://'.$this->apnsHost.':'.$this->apnsPort, $error, $errorString, 60, STREAM_CLIENT_CONNECT, $streamContext);

But know how to set SO_KEEPALIVE to true? I've also tried STREAM_CLIENT_PERSISTENT, which is not the same thing.

Answer 1

Have you verified (via network tracing) that you need to set the socket option?

What are you sending over the socket? HTTP/HTTPS introduces its own connection-reuse feature via the "Connection" header, so the option on the socket isn't necessarily what you want to set.

Answer 2

SO_KEEPALIVE like in

The SO_KEEPALIVE option causes a packet (called a 'keepalive probe') to be sent to the remote system if a long time (by default, more than 2 hours) passes with no other data being sent or received.

?
I don't know how this is related to STREAM_CLIENT_PERSISTENT but you can set that option with socket_set_option (i.e. using the sockets extension and not streams).