php实现协程，真正的异步

github上php的协程大部分是根据这篇文章实现的：http://nikic.github.io/2012/12/22/Cooperative-multitasking-using-coroutines-in-PHP.html。

它们最终的结果都是把回调变成了优雅的顺序执行的代码，但还是阻塞的，不是真正的异步。

比如最热门的：https://github.com/recoilphp/recoil

先安装：

composer require recoil/recoil：

执行：

<?php
//recoil.php

include __DIR__ . '/vendor/autoload.php';

use Recoil\React\ReactKernel;

$i = 100000;

ReactKernel::start(task1());
ReactKernel::start(task2());

function task1(){
    global $i;
    echo "wait start" . PHP_EOL;
    while ($i-- > 0) {
        yield;
    }
    echo "wait end" . PHP_EOL;
};

function task2(){
    echo "Hello " . PHP_EOL;
    yield;
    echo "world!" . PHP_EOL;
}

结果：
wait start
//等待若干秒
wait end
Hello
world!

我本来是想让两个任务并行，结果两个任务变成了串行，中间等待的时间什么事情都干不了。React响应式的编程是严格禁止这种等待的，所以我就参照unity3d的协程自己写了个php版本的。上代码：

<?php
//Coroutine.php
//依赖swoole实现的定时器，也可以用其它方法实现定时器

class Coroutine
{
    //可以根据需要更改定时器间隔，单位ms
    const TICK_INTERVAL = 1;

    private $routineList;

    private $tickId = -1;

    public function __construct()
    {
        $this->routineList = [];
    }

    public function start(Generator $routine)
    {
        $task = new Task($routine);
        $this->routineList[] = $task;
        $this->startTick();
    }

    public function stop(Generator $routine)
    {
        foreach ($this->routineList as $k => $task) {
            if($task->getRoutine() == $routine){
                unset($this->routineList[$k]);
            }
        }
    }

    private function startTick()
    {
        swoole_timer_tick(self::TICK_INTERVAL, function($timerId){
            $this->tickId = $timerId;
            $this->run();
        });
    }

    private function stopTick()
    {
        if($this->tickId >= 0) {
            swoole_timer_clear($this->tickId);
        }
    }

    private function run()
    {
        if(empty($this->routineList)){
            $this->stopTick();
            return;
        }

        foreach ($this->routineList as $k => $task) {
            $task->run();

            if($task->isFinished()){
                unset($this->routineList[$k]);
            }
        }
    }
    
}

class Task
{
    protected $stack;
    protected $routine;

    public function __construct(Generator $routine)
    {
        $this->routine = $routine;
        $this->stack = new SplStack();
    }

    /**
     * [run 协程调度]
     * @return [type]         [description]
     */
    public function run()
    {
        $routine = &$this->routine;

        try {

            if(!$routine){
                return;
            }

            $value = $routine->current(); 

            //嵌套的协程
            if ($value instanceof Generator) {
                $this->stack->push($routine);
                $routine = $value;
                return;
            }

            //嵌套的协程返回
            if(!$routine->valid() && !$this->stack->isEmpty()) {
                $routine = $this->stack->pop();
            }

            $routine->next();

        } catch (Exception $e) {

            if ($this->stack->isEmpty()) {
                /*
                    throw the exception 
                */
                return;
            }
        }
    }

    /**
     * [isFinished 判断该task是否完成]
     * @return boolean [description]
     */
    public function isFinished()
    {
        return $this->stack->isEmpty() && !$this->routine->valid();
    }

    public function getRoutine()
    {
        return $this->routine;
    }
}

测试代码：

<?php
//test.php

 require 'Coroutine.php';

$i = 10000;

$c = new Coroutine();
$c->start(task1());
$c->start(task2());

function task1(){
    global $i;
    echo "wait start" . PHP_EOL;
    while ($i-- > 0) {
        yield;
    }
    echo "wait end" . PHP_EOL;
};

function task2(){
    echo "Hello " . PHP_EOL;
    yield;
    echo "world!" . PHP_EOL;
}