protected function fill($placeholder, $instance){
        switch( $placeholder ){
            case 'title':
                return get_the_title();
                break;
            case 'url':
                return get_permalink();
                break;
            case 'excerpt':
                return  get_the_excerpt();
                break;
            case 'date':
                return  get_the_date();
                break;
            case 'modified':
                return get_the_modified_date();
                break;
            case 'author':
                return get_the_author();
                break;
            default:
                return false;
                break;
        }
    }