Piwik\SettingsPiwik::isPiwikInstalled PHP Method

    public static function isPiwikInstalled()
    {
        $config = Config::getInstance()->getLocalPath();
        $exists = file_exists($config);
        // Piwik is not installed if the config file is not found
        if (!$exists) {
            return false;
        }
        $general = Config::getInstance()->General;
        $isInstallationInProgress = false;
        if (array_key_exists('installation_in_progress', $general)) {
            $isInstallationInProgress = (bool) $general['installation_in_progress'];
        }
        if ($isInstallationInProgress) {
            return false;
        }
        // Check that the database section is really set, ie. file is not empty
        if (empty(Config::getInstance()->database['username'])) {
            return false;
        }
        return true;
    }

 public function configureTopMenu(MenuTop $menu)
 {
     if (Piwik::isUserIsAnonymous() || !SettingsPiwik::isPiwikInstalled()) {
         $langManager = new LanguagesManager();
         $menu->addHtml('LanguageSelector', $langManager->getLanguagesSelector(), true, $order = 30, false);
     }
 }