How to use WebSocket in PHP

With the development of network technology, WebSocket (Web Socket) has become a popular protocol, which can establish a real-time communication channel between the browser and the server to maintain a connection. This protocol plays a huge role in enabling real-time communication capabilities in web applications.

In the field of PHP development, WebSocket is used more and more widely. In this article, we will introduce how to use WebSocket in PHP.

1. Install WebSocket library

First, we need to use a PHP WebSocket library to easily implement WebSocket functions in PHP. Currently the most popular PHP WebSocket libraries are Ratchet and PHP WebSocket.

Here we use Ratchet, which uses the ReactPHP library to implement asynchronous event-driven PHP, and is perfectly compatible with other frameworks and has flexibility and scalability.

Before we start, we need to install Composer first, because Ratchet is installed and managed using Composer.

Composer can be downloaded here: https://getcomposer.org/

Install Ratchet using Composer:

composer require cboden/ratchet

2. Write a PHP WebSocket server

In this example, we are going to implement a simple chat room and use Ratchet to write a WebSocket server. The following are the steps to implement:

a. Create a WebSocket server

use RatchetServerIoServer;
use RatchetHttpHttpServer;
use RatchetWebSocketWsServer;

require dirname(__DIR__) . '/vendor/autoload.php';

$server = IoServer::factory(
    new HttpServer(
        new WsServer(
            new Chat()
        )
    ),
    8080
);

$server->run();

Here, the Ratchet library is first introduced, and then a WebSocket server is created. HttpServer and WsServer are used to specify HTTP and WebSocket protocol support respectively. and pass them to the Chat class (it will be shown later that the Chat class is used to handle client connection requests).

Here we listen to port 8080.

b. Create a chat room

use RatchetMessageComponentInterface;
use RatchetConnectionInterface;

class Chat implements MessageComponentInterface
{
    public $clients;

    public function __construct()
    {
        $this->clients = new SplObjectStorage;
    }

    public function onOpen(ConnectionInterface $conn)
    {
        $this->clients->attach($conn);
    }

    public function onMessage(ConnectionInterface $from, $msg)
    {
        foreach ($this->clients as $client) {
            if ($client !== $from) {
                $client->send($msg);
            }
        }
    }

    public function onClose(ConnectionInterface $conn)
    {
        $this->clients->detach($conn);
    }

    public function onError(ConnectionInterface $conn, Exception $e)
    {
        $conn->close();
    }
}

Here, we created a class named Chat, which implements the MessageComponentInterface interface. This interface defines the operations performed by the WebSocket server in different connection states.

Specifically, we declared a clients variable in the constructor, which is the SplObjectStorage object that stores the connected client. In the onOpen method, the connection object is assigned to this variable.

When there is a message from any client, we broadcast the message through the onMessage method, which will be received for each connection.

In the onClose method, the connection object will be removed from the variable. If an error occurs and the client connection cannot be handled, then our onError function will be called.

3. Write client-side JavaScript code

Next, we need client-side JavaScript code to connect to the WebSocket server.

let socket = new WebSocket('ws://localhost:8080');
socket.onopen = function(event) {
  console.log('WebSocket连接已建立');
};

socket.onmessage = function(event) {
  console.log('收到消息：' + event.data);
};

Here we directly use the API of the WebSocket object to connect and send and receive messages to the server.

4. Run the WebSocket Server

When you complete the above steps, you have successfully written a WebSocket server. Now run your server, either via the command line:

php server.php

When starting the server from the command line, you should see results similar to the following:

2019-03-22 11:46:55 WebSocketServer: Listening on 0.0.0.0:8080
2019-03-22 11:52:50 WebSocketServer: Opened connection to http://localhost:54616

indicates that the WebSocket service has started successfully And listen on port 8080.

5. Test the WebSocket connection

Finally, open the browser and visit http://localhost/chat.html. You can see that the browser connects and joins the WebSocket server.

let socket = new WebSocket('ws://localhost:8080');
socket.onopen = function(event) {
  console.log('WebSocket连接已建立');
  socket.send('欢迎加入聊天室');
};

socket.onmessage = function(event) {
  console.log('收到消息：' + event.data);
};

Here, we send the message to the server and log it in the console when the server message is received.

When running the test web page, you will see output similar to the following on the console:

WebSocket已连接
WebSocket收到消息：欢迎加入聊天室

Now, you have successfully used WebSocket in PHP and created a simple chat room. Hope this tutorial can be helpful to you.

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