class SessionManager
{
    public static function start(): void
    {
        if (session_status() === PHP_SESSION_NONE) {
            session_start();
        }
    }

    public static function set(string $key, mixed $value): void
    {
        self::start();
        $_SESSION[$key] = $value;
    }

    public static function get(string $key, mixed $default = null): mixed
    {
        self::start();
        return $_SESSION[$key] ?? $default;
    }

    public static function regenerate(): void
    {
        self::start();
        session_regenerate_id(true);
    }

    public static function destroy(): void
    {
        self::start();
        $_SESSION = [];
        session_destroy();
    }

    public static function isLoggedIn(): bool
    {
        return (bool) self::get('logged_in', false);
    }
}