Take you to understand the new features of generators in PHP7

Generator delegate

Simply translate the description of the official documentation:

In PHP7, through generator delegation (yield from), other generators, iterable objects, and arrays can be delegated to outer generators. The outer generator will first sequentially yield the delegated value, and then continue to yield the value defined in itself.

Using yield from can make it easier for us to write clearer generator nesting, and code nesting calls are necessary for writing complex systems.

The above example:

       
The above will output:
       
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
       
Naturally, the internal generator can also accept information or exceptions sent by its parent generator, because the yield from is Parent-child generators establish a bidirectional channel. Without further ado, here’s an example:
       
send($num); } $gen->send(null); foreach (range(1,5) as $num) { $gen->send($num); } //$gen->send("hello world"); //try it ,gay
       
The output is the same as the previous example.
       
Generator return value
       
If the generator is iterated, or runs to the return keyword, the generator will return a value.
There are two ways to obtain this return value:
       

        
Use the $ret = Generator::getReturn() method.
        
Use $ret = yield from Generator() expression.
       
       
The above example:
       
getReturn(); } foreach (task() as $item) { ; }
       
The output result will not be posted, everyone must have guessed it.
       
You can see that the combination of yield from and return makes the writing method of yield more like the synchronous mode code we usually write. After all, this is one of the reasons why PHP has the generator feature.
       
A non-blocking web server
       
Back in 2015, an article "Using Coroutines to Implement Multi-Task Scheduling in PHP" was reposted on Brother Bird's blog . The article introduces PHP5's iterative generator, coroutine, and implements a simple non-blocking web server. (See the link at the end of the article)
       
Now we use these two new features in PHP7 to rewrite this web server, which only requires more than 100 lines of code.
       
The code is as follows:
       
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 = <<