class Index {
    private static $_elements = array();
    private static $_idx = 0;

    private static $_prefix = ".";

    private static function add($element) {
        self::$_elements[self::$_idx] = $element;
        self::$_idx++;
    }

    public static function initialize() {
        $banner = new Banner(self::$_prefix);
        self::add($banner);
    }

    static public function show() {
        for ($i = 0; $i < self::$_idx; $i++) {
            self::$_elements[$i]->show();
        }
    }
}

Index::initialize();
Index::show();