PHP develops user group and subscription functions of real-time chat system

require 'vendor/autoload.php';

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

class Chat implements MessageComponentInterface {
    protected $clients;
    protected $groups;

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

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

    public function onMessage(ConnectionInterface $from, $msg) {
        // 处理收到的消息
    }

    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
);

$server->run();

public function joinGroup(ConnectionInterface $conn, $groupId) {
    // 将用户加入群组
    $this->groups[$groupId][] = $conn;
    echo "User ({$conn->resourceId}) joined group {$groupId}
";
}

public function leaveGroup(ConnectionInterface $conn, $groupId) {
    // 将用户从群组中移除
    $index = array_search($conn, $this->groups[$groupId]);
    if ($index !== false) {
        unset($this->groups[$groupId][$index]);
        echo "User ({$conn->resourceId}) left group {$groupId}
";
    }
}

public function subscribe(ConnectionInterface $conn, $topic) {
    // 订阅某个主题
    $conn->topics[] = $topic;
    echo "User ({$conn->resourceId}) subscribed to {$topic}
";
}

public function unsubscribe(ConnectionInterface $conn, $topic) {
    // 取消订阅某个主题
    $index = array_search($topic, $conn->topics);
    if ($index !== false) {
        unset($conn->topics[$index]);
        echo "User ({$conn->resourceId}) unsubscribed from {$topic}
";
    }
}

CREATE TABLE `users` (
  `id` int(11) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  `name` varchar(255) NOT NULL,
  `email` varchar(255) NOT NULL
);

CREATE TABLE `groups` (
  `id` int(11) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  `name` varchar(255) NOT NULL
);

CREATE TABLE `group_user` (
  `group_id` int(11) UNSIGNED NOT NULL,
  `user_id` int(11) UNSIGNED NOT NULL,
  PRIMARY KEY (`group_id`, `user_id`),
  FOREIGN KEY (`group_id`) REFERENCES `groups`(`id`),
  FOREIGN KEY (`user_id`) REFERENCES `users`(`id`)
);

public function joinGroup(ConnectionInterface $conn, $groupId) {
    // 将用户加入群组
    // ...

    // 将用户加入数据库
    $userId = $_SESSION['user_id']; // 假设用户登录时已经保存用户ID到session中
    $query = "INSERT INTO group_user (group_id, user_id) VALUES (?, ?)";
    $stmt = $mysqli->prepare($query);
    $stmt->bind_param("ii", $groupId, $userId);
    $stmt->execute();
}

public function subscribe(ConnectionInterface $conn, $topic) {
    // 订阅某个主题
    // ...

    // 将订阅信息保存到数据库
    $userId = $_SESSION['user_id'];
    $query = "INSERT INTO subscriptions (user_id, topic) VALUES (?, ?)";
    $stmt = $mysqli->prepare($query);
    $stmt->bind_param("is", $userId, $topic);
    $stmt->execute();
}