How to backup and restore data using real-time chat function using PHP

// 连接数据库
$db = new PDO("mysql:host=localhost;dbname=chat_app", "username", "password");

// 备份聊天记录
function backupChatData($from_user, $to_user, $message) {
    global $db;

    // 备份的表名
    $table_name = "chat_backup_" . date("Y_m_d");

    // 创建备份表（如果不存在）
    $create_table_sql = "CREATE TABLE IF NOT EXISTS {$table_name} (
                          `id` INT(11) AUTO_INCREMENT PRIMARY KEY,
                          `from_user` INT(11),
                          `to_user` INT(11),
                          `message` TEXT,
                          `created_at` DATETIME
                        )";
    $db->exec($create_table_sql);

    // 插入备份数据
    $insert_sql = "INSERT INTO {$table_name} (`from_user`, `to_user`, `message`, `created_at`)
                   VALUES (:from_user, :to_user, :message, NOW())";
    $stmt = $db->prepare($insert_sql);
    $stmt->bindParam(':from_user', $from_user);
    $stmt->bindParam(':to_user', $to_user);
    $stmt->bindParam(':message', $message);
    $stmt->execute();
}

// 备份新消息
backupChatData($from_user_id, $to_user_id, $message);

// 连接数据库
$db = new PDO("mysql:host=localhost;dbname=chat_app", "username", "password");

// 恢复聊天记录
function restoreChatData($backup_table_name) {
    global $db;

    // 检查备份表是否存在
    $check_table_sql = "SHOW TABLES LIKE '{$backup_table_name}'";
    $stmt = $db->query($check_table_sql);
    if ($stmt->rowCount() < 1) {
        return false;
    }

    // 创建主表（如果不存在）
    $create_main_table_sql = "CREATE TABLE IF NOT EXISTS chat_messages (
                                `id` INT(11) AUTO_INCREMENT PRIMARY KEY,
                                `from_user` INT(11),
                                `to_user` INT(11),
                                `message` TEXT,
                                `created_at` DATETIME
                              )";
    $db->exec($create_main_table_sql);

    // 恢复数据到主表
    $restore_sql = "INSERT INTO chat_messages (`from_user`, `to_user`, `message`, `created_at`)
                    SELECT `from_user`, `to_user`, `message`, `created_at`
                    FROM {$backup_table_name}";
    $db->exec($restore_sql);

    // 删除备份表
    $delete_table_sql = "DROP TABLE {$backup_table_name}";
    $db->exec($delete_table_sql);

    return true;
}

// 恢复备份数据
$backup_table_name = "chat_backup_" . date("Y_m_d");
restoreChatData($backup_table_name);