code: function pop($queue = null)
      {
          $queue = $this->_normalizeQueueName($queue);
  
          if (! isset($this->queues[$queue]) )
              return null;
  
          if ( null === $item = array_pop($this->queues[$queue]) )
              return null;
  
  
          $payload = $item['payload'];
          return $payload;
      }
docs: Pop From Queue
  
  note: when you pop a message from queue you have to
  release it when worker done with it.
  
  
  @param string $queue
  
  @return iPayloadQueued|null
  @throws exIOError