src/TransportUtil.php
public static function getBrowserUserAgentGenerated()
    {
        static $ua;
        if (isset($ua)) {
            return $ua;
        }

        $year  = abs(@date('Y'));
        if ($year <= 2017) {
            return $ua = self::DEFAULT_USER_AGENT;
        }

        $user_agent = 'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:[version].0) Gecko/20100101 Firefox/[version].0';
        $month      = abs(@date('m'));
        $version    = 51;
        $currentYear    = ($year-2017);
        $currentVersion = is_int($month/2) ? $month/2 : abs($month/2 + 0.5);
        $version   += $currentYear + $currentVersion;
        return $ua = str_replace('[version]', $version, $user_agent);
    }
public static function getBrowserUserAgentGenerated()
    {
        static $ua;
        if (isset($ua)) {
            return $ua;
        }

        $year  = abs(@date('Y'));
        if ($year <= 2017) {
            return $ua = self::DEFAULT_USER_AGENT;
        }

        $user_agent = 'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:[version].0) Gecko/20100101 Firefox/[version].0';
        $month      = abs(@date('m'));
        $version    = 51;
        $currentYear    = ($year-2017);
        $currentVersion = is_int($month/2) ? $month/2 : abs($month/2 + 0.5);
        $version   += $currentYear + $currentVersion;
        return $ua = str_replace('[version]', $version, $user_agent);
    }
Get generate User Agent

@return string