What are the implementation methods of non-blocking IO in PHP7.0?

PHP7.0 is a popular programming language that is widely used in web development and server-side development. One of the important updates is the introduction of non-blocking I/O. Non-blocking I/O is an asynchronous programming technique that can handle multiple I/O operations simultaneously without blocking the current thread. This technique greatly improves concurrency performance and responsiveness. This article will introduce the non-blocking I/O implementation in PHP7.0.

1. Stream Select

Stream Select is one of the simplest non-blocking I/O implementations in PHP7.0. This method uses the select system call to check whether all file streams (streams refer to open file handles, sockets, etc.) have readable data, and if so, read the data. This process is non-blocking and therefore does not block the current process.

The code for using Stream Select is as follows:

$read = array($fp);
$write = array();
$except = array();
if (false === ($num_changed_streams = stream_select($read, $write, $except, 0))) {
    die('Error Occured');
} elseif ($num_changed_streams > 0) {
    //有数据可读
    $data = fread($fp, $buffer_size);
} else {
    //无数据可读
}

The above code first uses the stream_select function to check whether there is readable data, and if so, reads the data. This check process is non-blocking and therefore does not block the current process.

2. Event Loop

Event Loop is another commonly used non-blocking I/O implementation in PHP7.0. The event loop implements non-blocking I/O operations by registering event callback functions, which are called when events occur. In the Event Loop, the application handles I/O operations by adding events and starting the event loop. For example, in web development, you can use Event Loop to handle HTTP requests.

The following is an example of using Event Loop to process HTTP requests:

$loop = ReactEventLoopFactory::create();
$client = new ReactHttpClientClient($loop);

$request = $client->request('GET', 'http://www.example.com/');
$request->on('response', function ($response) {
    $response->on('data', function ($chunk) {
        echo $chunk;
    });
});
$request->end();

$loop->run();

In the above example, an Event Loop object $loop based on ReactPHP is first created, and then an HTTP client $client is created , and initiate a GET request. In the callback function of the request response, use echo to output the received data.

3. Coroutine

Coroutine is another non-blocking I/O implementation introduced in PHP7.0. Coroutine takes advantage of the characteristics of coroutines to suspend the current coroutine and execute other coroutines when processing I/O operations. When the I/O operation is completed, the coroutine can resume running and continue executing the following code. This process is non-blocking.

The following is an example of using Coroutine to handle I/O operations:

$server = new SwooleServer("127.0.0.1", 9501, SWOOLE_PROCESS, SWOOLE_SOCK_TCP);

$server->on('Receive', function ($serv, $fd, $from_id, $data) {
    $result = "";
    $fp = stream_socket_client("tcp://127.0.0.1:80", $errno, $errstr, 30);
    fwrite($fp, $data);
    while (!feof($fp)) {
        $result .= fgets($fp, 1024);
    }
    fclose($fp);
    swoole_coroutine::sleep(0.1);
    $serv->send($fd, $result);
});

$server->start();

In the above code, first use the Swoole extension to create a TCP server object $server. In the callback function that receives client data, use the stream_socket_client function to initiate an HTTP request, and use a while loop to read the response data. During the process of reading data, use swoole_coroutine::sleep(0.1) to pause the execution of the current coroutine and wait for other coroutines to execute. When the response data is read successfully, the data is sent back to the client.

Conclusion

PHP7.0 introduces a variety of non-blocking I/O implementation methods, including Stream Select, Event Loop and Coroutine, etc. These technologies allow PHP applications to handle multiple I/O operations at the same time, improving concurrency performance and response speed. Many PHP frameworks and libraries, such as ReactPHP and Swoole, have integrated these non-blocking I/O technologies to help developers write high-performance web applications.

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