PHP apple push notification fail when multiple - php

Question

I have written a function to send push notifications to iOS devices. It sends pushes to more than 100 devices for now. However sometimes it is not sending push notifications. When I debug through the process I identified based on push notification the whole process fails. but the issues is all push tokens are in valid format. So my initial code was like this.
$certificatePath = CERTIFICATE_PATH . "/".APN_CERTIFICATE_FILE;
$streamContext = stream_context_create();
stream_context_set_option($streamContext, 'ssl', 'local_cert', $certificatePath);
stream_context_set_option($streamContext, 'ssl', 'passphrase', APN_PASSWORD);
$apns = stream_socket_client(APN_HOST . ':' . APN_PORT , $error, $errorString, 2, STREAM_CLIENT_CONNECT|STREAM_CLIENT_PERSISTENT, $streamContext);
if (!$apns) {
echo "Failed to connect $err $errstrn";
return false;
}
$payload = array();
$payload['aps'] = array('alert' =>$message,'title'=>$title, 'sound' => 'default','data'=>array());
$payload = json_encode($payload);
foreach ($pushTokens as $pushToken)
{
$pushToken = str_replace(' ', '', $pushToken);
if(!ctype_xdigit($pushToken))
continue;
$apnsMessage = chr(0) . pack("n",32) . pack('H*', str_replace(' ', '', $pushToken)) . pack ("n",strlen($payload)) . $payload;
$rst = fwrite($apns, $apnsMessage);
}
fclose($apns);
As a fix I changed the code to different way. I know this code is expensive since it open and close connection for every push notification.
$certificatePath = CERTIFICATE_PATH . "/".APN_CERTIFICATE_FILE;
$streamContext = stream_context_create();
stream_context_set_option($streamContext, 'ssl', 'local_cert', $certificatePath);
stream_context_set_option($streamContext, 'ssl', 'passphrase', APN_PASSWORD);
$payload = array();
$payload['aps'] = array('alert' =>$message,'title'=>$title, 'sound' => 'default','data'=>array());
$payload = json_encode($payload);
foreach ($pushTokens as $pushToken)
{
$apns = stream_socket_client(APN_HOST . ':' . APN_PORT , $error, $errorString, 2, STREAM_CLIENT_CONNECT|STREAM_CLIENT_PERSISTENT, $streamContext);
if (!$apns) {
echo "Failed to connect $err $errstrn";
return false;
}
$pushToken = str_replace(' ', '', $pushToken);
if(!ctype_xdigit($pushToken))
continue;
$apnsMessage = chr(0) . pack("n",32) . pack('H*', str_replace(' ', '', $pushToken)) . pack ("n",strlen($payload)) . $payload;
$rst = fwrite($apns, $apnsMessage);
fclose($apns);
}
I am wondering if it is an issue with fwrite or somewhere else. Appreciate if someone can help me with my first method as it is speed, and run with minimum resources.