Multiple socket poller in PHP

<?php
/*
* Reading from multiple sockets
* This version uses zmq_poll()
* @author Ian Barber <ian(dot)barber(at)gmail(dot)com>
*/

$context = new ZMQContext();

// Connect to task ventilator
$receiver = new ZMQSocket($context, ZMQ::SOCKET_PULL);
$receiver->connect("tcp://localhost:5557");

// Connect to weather server
$subscriber = new ZMQSocket($context, ZMQ::SOCKET_SUB);
$subscriber->connect("tcp://localhost:5556");
$subscriber->setSockOpt(ZMQ::SOCKOPT_SUBSCRIBE, "10001");

// Initialize poll set
$poll = new ZMQPoll();
$poll->add($receiver, ZMQ::POLL_IN);
$poll->add($subscriber, ZMQ::POLL_IN);

$readable = $writeable = array();

// Process messages from both sockets
while (true) {
$events = $poll->poll($readable, $writeable);
if ($events > 0) {
foreach ($readable as $socket) {
if ($socket === $receiver) {
$message = $socket->recv();
// Process task
} elseif ($socket === $subscriber) {
$mesage = $socket->recv();
// Process weather update
}
}
}
}

// We never get here