APNS Failed to connect: 0 - php

Question

I followed Ray Wenderlich's tutorial for remote notifications on iOS, and had no issues with development. In production, however, my notifications are failing with the error: Failed to connect: 0
I've searched around, but nobody seems to have a definitive script, and many of the answers on SO are contradictory. Here is the code I am currently using:
<?php
// Put your device token here (without spaces):
$deviceToken = [my device token];
// Put your private key's passphrase here:
// ITS REALLY THE PEM PASS
$passphrase = [the password];
// Put your alert message here:
$message = 'Hello, User!';
////////////////////////////////////////////////////////////////////////////////
$ctx = stream_context_create();
$cert = __DIR__ . '/Notifications_iOS/ck.pem';
stream_context_set_option($ctx, 'ssl', 'local_cert', $cert);
stream_context_set_option($ctx, 'ssl', 'passphrase', $passphrase);
// Open a connection to the APNS server
/*
// Dev
$fp = stream_socket_client(
'ssl://gateway.sandbox.push.apple.com:2195', $err,
$errstr, 60, STREAM_CLIENT_CONNECT|STREAM_CLIENT_PERSISTENT, $ctx);
*/
// Production
$fp = stream_socket_client(
'ssl://gateway.push.apple.com:2195', $err,
$errstr, 60, STREAM_CLIENT_CONNECT|STREAM_CLIENT_PERSISTENT, $ctx);
if (!$fp)
exit("Failed to connect: $err $errstr" . PHP_EOL);
echo 'Connected to APNS' . PHP_EOL;
// Create the payload body
$body['aps'] = array(
'alert' => $message,
'sound' => 'default'
);
// Encode the payload as JSON
$payload = json_encode($body);
// Build the binary notification
$msg = chr(0) . pack('n', 32) . pack('H*', $deviceToken) . pack('n', strlen($payload)) . $payload;
// Send it to the server
$result = fwrite($fp, $msg, strlen($msg));
if (!$result)
echo 'Message not delivered' . PHP_EOL;
else
echo 'Message successfully delivered' . PHP_EOL;
// Close the connection to the server
fclose($fp);
?>