public function __isset($key)
    {
        switch ($key) {
            case 'id':
            case 'network_id':
                return true;
            case 'blogname':
            case 'siteurl':
            case 'post_count':
            case 'home':
                if (! did_action('ms_loaded')) {
                    return false;
                }
                return true;
            default: // Custom properties added by 'site_details' filter.
                if (! did_action('ms_loaded')) {
                    return false;
                }

                $details = $this->get_details();
                if (isset($details->$key)) {
                    return true;
                }
        }

        return false;
    }