set_time_limit(0); //這句很重要, 不至于運行超時
while (true) {
  if (hasNewMessage()) {
    echo json_encode(getNewMessage());
    break;
  }
  usleep(100000);   //避免太過頻繁的查詢
}

<script type="text/javascript">
  (function longPolling() {
    $.ajax({
      'url': 'server.php',
      'data': data,
      'dataType': 'json',
      'success': function(data) {
        processData(data);
        longPolling();
      },
      'error': function(data) {
        longPolling();
      }
    });
  })();
</script>

<?php
namespace church\LongPolling;
use Closure;
use church\LongPolling\Queue\RedisQueue;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\JsonResponse;
class Server
{
  public $event = [];
  public $redisQueue = null;
  public $request = null;
  public $response = null;
  public function __construct()
  {
    $this->redisQueue = new RedisQueue();
    $this->request = Request::createFromGlobals();
    $this->response = new JsonResponse();
  }
  public function on($event, Closure $closure)
  {
    if (is_callable($closure)) {
      $this->event[$event][] = $closure;
    }
  }
  public function fire($event)
  {
    if (isset($this->event[$event])) {
      foreach ($this->event[$event] as $callback) {
        call_user_func($callback, $this);
      }
    }
  }
  public function sendMessage($data)
  {
    switch ($data['type']) {
      case 'unicast':   //單播
        $this->unicast($data['target'], $data['data'], $data['resource']);
        break;
      case 'multicast':    //組播
        foreach ($data['target'] as $target) {
          $this->unicast($target, $data['data'], $data['resource']);
        }
        break;
      case 'broadcast':    //廣播
        foreach ($this->redisQueue->setQueueName('connections') as $target) {
          $this->unicast($target, $data['data'], $data['resource']);
        }
        break;
    }
    $this->fire('message');
  }
  public function unicast($target, $message, $resource = 'system')
  {
    $redis_queue = new RedisQueue();
    $redis_queue->setQueueName($target)->push($resource . ':' . $message);
  }
  public function getMessage($target)
  {
    return $this->redisQueue->setQueueName($target)->pop();
  }
  public function hasMessage($target)
  {
    return count($this->redisQueue->setQueueName($target));
  }
  public function run()
  {
    $data = $this->request->request;
    while (true) {
      if ($data->get('action') == 'getMessage') {
        if ($this->hasMessage($data->get('target'))) {
          $this->response->setData([
            'state' => 'ok',
            'message' => '獲取成功',
            'data' => $this->getMessage($data->get('target'))
          ]);
          $this->response->send();
          break;
        }
      } elseif ($data->get('action') == 'connect') {
        $exist = false;
        foreach ($this->redisQueue->setQueueName('connections') as $connection) {
          if ($connection == $data->get('data')) {
            $exist = true;
          }
        }
        if (! $exist) {
          $this->redisQueue->setQueueName('connections')->push($data->get('data'));
        }
        $this->fire('connect');
        break;
      }
      usleep(100000);
    }
  }
}