queue = new SplQueue(); } /** * Add a callback to be invoked on a future tick of the event loop. * * Callbacks are guaranteed to be executed in the order they are enqueued. * * @param callable $listener The callback to invoke. */ public function add($listener) { $this->queue->enqueue($listener); } /** * Flush the callback queue. */ public function tick() { // Only invoke as many callbacks as were on the queue when tick() was called. $count = $this->queue->count(); while ($count--) { \call_user_func($this->queue->dequeue()); } } /** * Check if the next tick queue is empty. * * @return boolean */ public function isEmpty() { return $this->queue->isEmpty(); } }