广告：宝塔Linux面板高效运维的服务器管理软件 点击【 https://www.bt.cn/p/uNLv1L 】立即购买

生成器委托

简单地翻译官方文档的描述：

PHP7中，通过生成器委托（yield from），可以将其他生成器、可迭代的对象、数组委托给外层生成器。外层的生成器会先顺序 yield 委托出来的值，然后继续 yield 本身中定义的值。

利用 yield from 可以方便我们编写比较清晰生成器嵌套，而代码嵌套调用是编写复杂系统所必需的。

上例子：

<?phpfunction echoTimes($msg, $max) {    for ($i = 1; $i <= $max; ++$i) {        echo "$msg iteration $i\n";        yield;    }} function task() {    yield from echoTimes('foo', 10); // print foo ten times    echo "---\n";    yield from echoTimes('bar', 5); // print bar five times}foreach (task() as $item) {    ;}

以上将输出：

foo iteration 1foo iteration 2foo iteration 3foo iteration 4foo iteration 5foo iteration 6foo iteration 7foo iteration 8foo iteration 9foo iteration 10---bar iteration 1bar iteration 2bar iteration 3bar iteration 4bar iteration 5

自然，内部生成器也可以接受它的父生成器发送的信息或者异常，因为 yield from 为父子生成器建立一个双向的通道。不多说，上例子：

<?phpfunction echoMsg($msg) {    while (true) {        $i = yield;        if($i === null){            break;        }        if(!is_numeric($i)){            throw new Exception("Hoo! must give me a number");        }        echo "$msg iteration $i\n";    }}function task2() {    yield from echoMsg('foo');    echo "---\n";    yield from echoMsg('bar');}$gen = task2();foreach (range(1,10) as $num) {    $gen->send($num);}$gen->send(null);foreach (range(1,5) as $num) {    $gen->send($num);}//$gen->send("hello world"); //try it ,gay

输出和上个例子是一样的。

生成器返回值

如果生成器被迭代完成，或者运行到 return 关键字，是会给这个生成器返回值的。可以有两种方法获取这个返回值：

上例子：

<?phpfunction echoTimes($msg, $max) {    for ($i = 1; $i <= $max; ++$i) {        echo "$msg iteration $i\n";        yield;    }    return "$msg the end value : $i\n";}function task() {    $end = yield from echoTimes('foo', 10);    echo $end;    $gen = echoTimes('bar', 5);    yield from $gen;    echo $gen->getReturn();}foreach (task() as $item) {    ;}

输出结果就不贴了，想必大家都猜到。

可以看到 yield from 和 return 结合使得 yield 的写法更像平时我们写的同步模式的代码了，毕竟，这就是 PHP 出生成器特性的原因之一呀。

一个非阻塞的web服务器

时间回到2015年，鸟哥博客上转载的一篇《 在PHP中使用协程实现多任务调度》。文章介绍了PHP5 的迭代生成器，协程，并实现了一个简单的非阻塞 web 服务器。（链接见文末引用）

现在我们利用 PHP7 中的这两个新特性重写这个 web 服务器，只需要 100 多行代码。

代码如下：

<?phpclass CoSocket{    protected $masterCoSocket = null;    public $socket;    protected $handleCallback;    public $streamPoolRead = [];    public $streamPoolWrite = [];    public function __construct($socket, CoSocket $master = null)    {        $this->socket = $socket;        $this->masterCoSocket = $master ?? $this;    }    public function accept()    {        $isSelect = yield from $this->onRead();        $acceptS = null;        if ($isSelect && $as = stream_socket_accept($this->socket, 0)) {            $acceptS = new CoSocket($as, $this);        }        return $acceptS;    }    public function read($size)    {        yield from $this->onRead();        yield ($data = fread($this->socket, $size));        return $data;    }    public function write($string)    {        yield from $this->onWriter();        yield fwrite($this->socket, $string);    }    public function close()    {        unset($this->masterCoSocket->streamPoolRead[(int)$this->socket]);        unset($this->masterCoSocket->streamPoolWrite[(int)$this->socket]);        yield ($success = @fclose($this->socket));        return $success;    }    public function onRead($timeout = null)    {        $this->masterCoSocket->streamPoolRead[(int)$this->socket] = $this->socket;        $pool = $this->masterCoSocket->streamPoolRead;        $rSocks = [];        $wSocks = $eSocks = null;        foreach ($pool as $item) {            $rSocks[] = $item;        }        yield ($num = stream_select($rSocks, $wSocks, $eSocks, $timeout));        return $num;    }    public function onWriter($timeout = null)    {        $this->masterCoSocket->streamPoolWrite[(int)$this->socket] = $this->socket;        $pool = $this->masterCoSocket->streamPoolRead;        $wSocks = [];        $rSocks = $eSocks = null;        foreach ($pool as $item) {            $wSocks[] = $item;        }        yield ($num = stream_select($rSocks, $wSocks, $eSocks, $timeout));        return $num;    }    public function onRequest()    {        /** @var self $socket */        $socket = yield from $this->accept();        if (empty($socket)) {            return false;        }        $data = yield from $socket->read(8192);        $response = call_user_func($this->handleCallback, $data);        yield from $socket->write($response);        return yield from $socket->close();    }    public static function start($port, callable $callback)    {        echo "Starting server at port $port...\n";        $socket = @stream_socket_server("tcp://0.0.0.0:$port", $errNo, $errStr);        if (!$socket) throw new Exception($errStr, $errNo);        stream_set_blocking($socket, 0);        $coSocket = new self($socket);        $coSocket->handleCallback = $callback;        function gen($coSocket)        {            /** @var self $coSocket */            while (true) yield from $coSocket->onRequest();        }        foreach (gen($coSocket) as $item){};    }}CoSocket::start(8000, function ($data) {    $response = <<<RESHTTP/1.1 200 OKContent-Type: text/plainContent-Length: 12Connection: closehello world!RES;    return $response;});