how to display part of a menu tree?

Question

I\'m trying to deal with Wordpress 3.0. It\'s rather cool thing but I can\'t get on with one problem. For example, I have such menu tree. Menu tree is constructed from pages

Answer 1

have you seen wp_list_pages?

http://codex.wordpress.org/Function_Reference/wp_list_pages

look closer on child_of attribute

Answer 2

You can write a filter_hook to accomplish this.

My method: create an additional start_in argument for wp_nav_menu using my custom hook:

# in functions.php add hook & hook function
add_filter("wp_nav_menu_objects",'my_wp_nav_menu_objects_start_in',10,2);

# filter_hook function to react on start_in argument
function my_wp_nav_menu_objects_start_in( $sorted_menu_items, $args ) {
    if(isset($args->start_in)) {
        $menu_item_parents = array();
        foreach( $sorted_menu_items as $key => $item ) {
            // init menu_item_parents
            if( $item->object_id == (int)$args->start_in ) $menu_item_parents[] = $item->ID;

            if( in_array($item->menu_item_parent, $menu_item_parents) ) {
                // part of sub-tree: keep!
                $menu_item_parents[] = $item->ID;
            } else {
                // not part of sub-tree: away with it!
                unset($sorted_menu_items[$key]);
            }
        }
        return $sorted_menu_items;
    } else {
        return $sorted_menu_items;
    }
}

Next, in your template you just call wp_nav_menu with the additional start_in argument containing the ID of the page you want the children off:

wp_nav_menu( array( 
    'theme_location' => '<name of your menu>',
    'start_in' => $ID_of_page,
    'container' => false,
    'items_wrap' => '%3$s'
) );

Answer 3

Check out wp_list_pages(). It is useful for providing child navigation in the sidebar.

Answer 4

I wrote this to print sub-navs of the pages you may be on. If you want to print out the sub-navigation for each of the pages, get the page parent instead of getting the ID. There would be more involved than that, but it's a start.

$menu = wp_get_nav_menu_items( 'Primary Menu' );
$post_ID = get_the_ID();
echo "<ul id='sub-nav'>";
foreach ($menu as $item) {
    if ($post_ID == $item->object_id) { $menu_parent = $item->ID; }
    if (isset($menu_parent) && $item->menu_item_parent == $menu_parent) {
         echo "<li><a href='" . $item->url . "'>". $item->title . "</a></li>";
     }
 }
echo "</ul>";`

Answer 5

mac joost's answer is great, but I would add that if you want the parent item to print, then you shouldn't unset the parent, so line 18 needs to be adjusted accordingly:

    if($item->object_id != (int)$args->start_in) { unset($sorted_menu_items[$key]); }

Answer 6

I've stopped to explore how to output custom part of worpress site taxonomy on the server-side. I just use jquery to copy active taxonomy branch from main menu and paste it to the page container I need.