public function is_installed_and_upgraded() {
        if (!$this->rootdir) {
            return false;
        }
        if ($this->versiondb === null and $this->versiondisk === null) {
            // There is no version.php or version info inside it.
            return false;
        }

        return ((float)$this->versiondb === (float)$this->versiondisk);
    }