php 多线程 worker 类中的 collect方法

<?php/** * Created by PhpStorm. * User: 27394 * Date: 2017/4/18 * Time: 8:50 */// Worker 线程：非指定，不自动结束class Test extends Threaded{    // TODO}$worker = new Worker();echo "当前任务栈中包含 {$worker->collect()}任务\n";for ($i = 0; $i < 3; ++$i) {    $worker->stack(new Test());}echo "当前任务栈中包含 {$worker->collect()}任务\n";$worker->start();while ($worker->collect());// 阻塞直到线程结束echo "当前任务栈中包含 {$worker->collect()}任务\n";$worker->shutdown();`这里写代码片`