private function openBrowser($url)
    {
        $url = ProcessExecutor::escape($url);

        if (defined('PHP_WINDOWS_VERSION_MAJOR')) {
            return passthru('start "web" explorer "' . $url . '"');
        }

        passthru('which xdg-open', $linux);
        passthru('which open', $osx);

        if (0 === $linux) {
            passthru('xdg-open ' . $url);
        } elseif (0 === $osx) {
            passthru('open ' . $url);
        } else {
            $this->getIO()->writeError('no suitable browser opening command found, open yourself: ' . $url);
        }
    }