官方最新版本（2.6.0）已经解决了这个问题，可以达到子菜单级别的高亮：
` /**

 * Checks whether a menu item is active.
 * This is done by checking if [[route]] and [[params]] match that specified in the `url` option of the menu item.
 * When the `url` option of a menu item is specified in terms of an array, its first element is treated
 * as the route for the item and the rest of the elements are the associated parameters.
 * Only when its route and parameters match [[route]] and [[params]], respectively, will a menu item
 * be considered active.
 * @param array $item the menu item to be checked
 * @return boolean whether the menu item is active
 */
protected function isItemActive($item)
{
    if (isset($item['url']) && is_array($item['url']) && isset($item['url'][0])) {
        $route = $item['url'][0];
        if ($route[0] !== '/' && Yii::$app->controller) {
            $route = ltrim(Yii::$app->controller->module->getUniqueId() . '/' . $route, '/');
        }
        $route = ltrim($route, '/');
        if ($route != $this->route && $route !== $this->noDefaultRoute && $route !== $this->noDefaultAction) {
            return false;
        }
        unset($item['url']['#']);
        if (count($item['url']) > 1) {
            foreach (array_splice($item['url'], 1) as $name => $value) {
                if ($value !== null && (!isset($this->params[$name]) || $this->params[$name] != $value)) {
                    return false;
                }
            }
        }
        return true;
    }
    return false;
}`