Contao\CoreBundle\Cache\ContaoCacheWarmer::getLanguagesInUse PHP Method

    private function getLanguagesInUse()
    {
        // Get all languages in use (see #6013)
        $query = "\n            SELECT language FROM tl_member\n            UNION SELECT language FROM tl_user\n            UNION SELECT REPLACE(language, '-', '_') FROM tl_page\n            WHERE type='root'\n        ";
        $statement = $this->connection->prepare($query);
        $statement->execute();
        $languages = [];
        while (false !== ($language = $statement->fetch(\PDO::FETCH_OBJ))) {
            if ('' === $language->language) {
                continue;
            }
            $languages[] = $language->language;
            // Also cache "de" if "de-CH" is requested
            if (strlen($language->language) > 2) {
                $languages[] = substr($language->language, 0, 2);
            }
        }
        return array_unique($languages);
    }