How to Send Realtime Notifications if User Follow using PHP & Mysql

Hello there, in this tutorial we will learn how to send real-time notifications to a user when someone follows them, you can use a combination of PHP and MySQL along with a WebSocket connection. Here are the steps:

1. Create a database table to store the followers information. The table should have at least three columns: id, follower_id, and user_id. The id column should be an auto-increment primary key, follower_id column should store the id of the user who is following, and user_id column should store the id of the user who is being followed.

2. Create a PHP script that inserts a new row into the followers table whenever a user follows another user. This script should take the follower_id and user_id as parameters and insert them into the followers table.

3. Create a WebSocket server that listens for new follower events. Whenever a new follower event occurs, the server should broadcast a notification to the user who is being followed. You can use a library like Ratchet to create a WebSocket server in PHP.

4. Modify the PHP script that inserts a new row into the followers table to also send a new follower event to the WebSocket server. This can be done using a library like Guzzle to make an HTTP request to the WebSocket server.

5. Create a JavaScript client that listens for new follower notifications and displays them to the user. This can be done using a library like Socket.IO to create a WebSocket connection between the client and the server.

Here's an example PHP code that inserts a new follower into the database and sends a notification to the WebSocket server:

<?php

// Connect to the database
$db = new mysqli('localhost', 'username', 'password', 'database');

// Get the follower_id and user_id from the POST request
$follower_id = $_POST['follower_id'];
$user_id = $_POST['user_id'];

// Insert a new row into the followers table
$stmt = $db->prepare("INSERT INTO followers (follower_id, user_id) VALUES (?, ?)");
$stmt->bind_param('ii', $follower_id, $user_id);
$stmt->execute();

// Send a notification to the WebSocket server
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://localhost:8000/new-follower');
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode([
    'user_id' => $user_id,
]));
curl_exec($ch);
curl_close($ch);

?>

And here's an example WebSocket server code that broadcasts a new follower notification to all connected clients:

<?php

use Ratchet\MessageComponentInterface;
use Ratchet\ConnectionInterface;

class FollowerServer implements MessageComponentInterface {
    protected $clients;

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

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

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

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

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

$server = new \Ratchet\App('localhost', 8000);
$server->route('/new-follower', new class implements MessageComponentInterface {
    protected $clients;

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

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