How to use PHP to implement long links

When using PHP to develop network applications, it is often necessary to use long links to achieve real-time communication and interaction with the server. This article introduces how to use PHP to implement long links.

Long Connection, also known as Persistent Connection, refers to a connection established between the client and the server that remains open once established until the client or server is disconnected. Open connection. In this way, the client can send requests or data to the server at any time through this connection, and the server can also push data or events to the client at any time.

The main advantage of long connections is that it has a stronger ability to handle concurrent connections, which can reduce the burden on the server and improve the performance and response speed of applications; secondly, long connections can also be implemented in real-time communication and push tasks Lower latency and real-time performance.

The following is an example of a simple long link implementation:

// 客户端代码
$socket = fsockopen("127.0.0.1", 8888, $errno, $errstr, 30);
if (!$socket) {
    echo "$errstr ($errno)\n";
} else {
    fwrite($socket, "GET / HTTP/1.1\r\nHost: example.com\r\nConnection: Keep-Alive\r\n\r\n");
    while (!feof($socket)) {
        echo fgets($socket, 128);
    }
    fclose($socket);
}

// 服务器端代码
$server = stream_socket_server("tcp://0.0.0.0:8888", $errno, $errstr);
if (!$server) {
    echo "$errstr ($errno)\n";
} else {
    while (true) {
        $client = stream_socket_accept($server);
        if ($client) {
            while ($data = fread($client, 4096)) {
                // 处理接收到的数据或请求事件
                echo $data;
            }
            fclose($client);
        }
    }
    fclose($server);
}

In the client code, first use the fsockopen function to connect to the server, and send an HTTP GET request, and maintain the connection status ( Connection: Keep-Alive), and then continuously read and output the data received from the server through a while loop until the end symbol (feof) is read or the server closes the connection. In the server-side code, first use the stream_socket_server function to create a TCP server bound to port 8888, then use the stream_socket_accept function to accept the client's request, and continuously read the data transmitted from the client through the while loop, and process the received data or request events, and then wait for the client's request again.

It should be noted here that in actual applications, we usually do not use these two functions directly to implement long links, but need to carry out certain encapsulation and processing at the code level in order to better Control and manage the connection status and data transmission of long links. In addition, there are some open source frameworks and components in PHP, such as Swoole, Workerman, etc., which can easily implement the functions of long links and high concurrency processing, which not only improves development efficiency, but also optimizes performance and stability.

In short, long links have a wide range of application scenarios in Web development, which can improve the performance and real-time nature of applications. For application scenarios that require real-time interaction, push, notification and other tasks, long links will be a Very effective solution.

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