Create a real-time chat application using PHP and WebSocket

With the development of the Internet, the demand for real-time communication is also increasing. Live chat apps are popular for their immediacy and convenience. This article will show you how to create a reliable real-time chat application using PHP and WebSocket.

What is WebSocket?

WebSocket is a protocol for full-duplex communication between a web browser and a web server. This means that it allows two-way communication with the server instead of requests and responses via the HTTP protocol. Using WebSocket, efficient, real-time communication is possible, which is very important for real-time chat applications.

How to create a WebSocket server using PHP

In order to create a WebSocket server, we will use the Ratchet library. Ratchet is a PHP WebSocket library based on Symfony components that can help us create WebSocket servers quickly and easily. To use Ratchet, you need to install Composer in PHP, which is a PHP application dependency manager. If you don't have Composer installed yet, install it first.

Create a new PHP project folder and use the following Composer command to install Ratchet:

composer require cboden/ratchet

Once Ratchet is installed, we can start writing the WebSocket server code. The following is a simple example:

<?php
require __DIR__ . '/vendor/autoload.php';

use RatchetMessageComponentInterface;
use RatchetConnectionInterface;
use RatchetServerIoServer;
use RatchetHttpHttpServer;
use RatchetWebSocketWsServer;

class Chat implements MessageComponentInterface {
    protected $clients;

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

    public function onOpen(ConnectionInterface $conn) {
        $this->clients->attach($conn);
        echo "New connection! ({$conn->resourceId})
";
    }

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

    public function onClose(ConnectionInterface $conn) {
        $this->clients->detach($conn);
        echo "Connection {$conn->resourceId} has disconnected
";
    }

    public function onError(ConnectionInterface $conn, Exception $e) {
        echo "An error has occurred: {$e->getMessage()}
";
        $conn->close();
    }
}

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

echo "Server started at port 8080...
";

$server->run();

In this example, we define a class named "Chat" that implements Ratchet's MessageComponentInterface interface. We use SplObjectStorage to store client connections, and when a client connects to the server, we use the onOpen() function to attach it to the storage. When a message is sent to the server, we use the onMessage() function to send the message to all other clients. When the client disconnects, we use the onClose() function to remove the client from the storage.

Finally, we use the IoServer class to bind the WebSocket server to port 8080 and start the server. Now, we have successfully created a simple WebSocket server and can connect it to a web browser by using the JavaScript WebSocket API.

How to create a client using JavaScript and WebSocket API

Now that we have a WebSocket server, we need to write JavaScript code to connect to it. We will use WebSocket API.

The following is a simple WebSocket client example:

let ws = new WebSocket('ws://localhost:8080');

ws.onopen = () => {
    console.log('Connected to WebSocket server');
};

ws.onmessage = evt => {
    console.log('Received message: ' + evt.data);
};

ws.onclose = () => {
    console.log('Disconnected from WebSocket server');
};

ws.onerror = error => {
    console.error('WebSocket error: ' + error);
};

function sendMsg() {
    let input = document.getElementById('message');
    let msg = input.value;
    ws.send(msg);
    input.value = '';
}

We use the WebSocket constructor to create a new WebSockets instance and connect it to the specified WebSocket server. We use onopen, onmessage, onclose and onerror event handlers to handle different states and messages of WebSocket. We also define a function called "sendMsg" to send user-entered messages to the server. This function calls WebSocket's send() function to send data.

Finally, we need to create a simple form in the HTML page with text input and a send button so that we can send the message. Here is the HTML code:

<!DOCTYPE html>
<html>
<head>
    <title>WebSocket Chat App</title>
    <script src="chat.js"></script>
</head>
<body>
    <h1>WebSocket Chat App</h1>
    <div id="messages"></div>
    <input type="text" id="message">
    <button onclick="sendMsg()">Send</button>
</body>
</html>

By using an HTML page with JavaScript code, we can now create a complete live chat application. When the user enters a message in the browser and clicks the send button, the message is sent to the server via WebSocket and displayed in all other browsers with connected clients.

Summary

In this article, we created a real-time chat application using PHP and WebSocket. We use the Ratchet library to quickly create a WebSocket server and the JavaScript WebSocket API to create the client. Using Ratchet and WebSocket API, we can easily achieve efficient, real-time communication to create reliable real-time chat applications.

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