hierarchy navigation items

function hier_nav($root) {
    global $post;

    if(is_string($root))
        $return['first'] = get_page_by_path($root);

    $pages = get_pages(array(
        'child_of' => $return['first'] ? $return['first']->ID : 0,
        'sort_order' => 'ASC',
        'sort_column' => 'menu_order',
        'hierarchical' => 1,
        'parent' => -1,
        'post_type' => 'page',
        'post_status' => 'publish'
    ));

    foreach($pages as $page){
        if($page->ID == $post->post_parent){
            $return['up'] = $page;
        }elseif($page->post_parent == $post->ID){
            $return['children'][] = $page;
        }

        if($page->ID == $post->ID){
            $return['here'] = $page;
        }elseif($return['here']){
            $return['next'] = $page;
            $return['last'] = end($pages);
            break;
        }else{
            $return['prev'] = $page;
        }
    }
    if(!$return['prev'])
        $return['prev'] = $return['first'];

    return $return;
}