產生器委託
簡單翻譯官方文件的描述：#在
利用 yield from 可以方便我們編寫比較清晰生成器嵌套，而程式碼巢狀呼叫是編寫複雜系統所必需的。 上例：##PHP7中，透過生成器委託（yield from），可以將其他生成器、可迭代的物件、陣列委託給外層產生器。外層的生成器會先順序 yield 委託出來的值，然後繼續 yield 本身定義的值。
<?php function 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 $item) {
;
}以上將輸出：foo iteration 1 foo iteration 2 foo iteration 3 foo iteration 4 foo iteration 5 foo iteration 6 foo iteration 7 foo iteration 8 foo iteration 9 foo iteration 10 --- bar iteration 1 bar iteration 2 bar iteration 3 bar iteration 4 bar iteration 5自然，內部產生器也可以接受它的父產生器所傳送的訊息或異常，因為yield from 為父子生成器建立一個雙向的通道。不多說，上例子：
<?php function echoMsg($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輸出和上個例子是一樣的。 產生器回傳值
如果生成器被迭代完成，或是執行到 return 關鍵字，是會給這個生成器回傳值的。可以有兩種方法來取得這個回傳值：
- 使用 $ret = Generator::getReturn() 方法。
- 使用 $ret = yield from Generator() 表達式。
<?php function echoTimes($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) {
;
}輸出結果就不貼了，想必大家都猜到。 可以看到 yield from 和 return 結合使得 yield 的寫法更像平常我們寫的同步模式的程式碼了，畢竟，這就是 PHP 出生成器特性的原因之一呀。 一個非阻塞的web伺服器
時間回到2015年，鳥哥部落格上轉載的一篇《 在PHP中使用協程實現多任務調度》 。文章介紹了PHP5 的迭代產生器，協程，並實作了一個簡單的非阻塞 web 伺服器。 （連結見文末引用）現在我們利用 PHP7 中的這兩個新功能重寫這個 web 伺服器，只需要 100 多行程式碼。 程式碼如下：<?php class 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 = 
