public static function useSocks5($host, $port = 1080, $user = null, $pass = null)
    {
        if ($host === null) {
            self::$_socks5 = [];
        } else {
            self::$_socks5 = ['conn' => 'tcp://' . $host . ':' . $port];
            if ($user !== null && $pass !== null) {
                self::$_socks5['user'] = $user;
                self::$_socks5['pass'] = $pass;
            }
        }
    }