WordPress wp_nav_menu specific sub menu only - wordpress

Question

I want to create a menu that pulls only the sub-menu options for a particular page.
For example, if the menu option DASHBOARD has the sub-menus MESSAGE BOARD and CALENDAR, I want to be able to create a separate menu with just MESSAGE BOARD and CALENDAR.
I'd like to do this without the wp_list_pages function so that the menu options can be managed using the Appearances > Menus tab in WordPress.
Thanks!

Answer 1

If I understood you correctly, you want additional menu items for sub pages?
I.E. You have a menu that looks like this
HOME ABOUT DASHBOARD FAQ CONTACT
DASHBOARD has 2 sub-pages -> BOARD CALENDAR
When you are on the DASHBOARD page you want the BOARD and CALENDAR pagees to show like this:
HOME ABOUT DASHBOAR FAQ CONTACT
BOARD CALENDAR
You can add an aditional menu in functions.php like this
<?php if (function_exists('register_nav_menus'))
{
register_nav_menus
(
array
(
'main_nav'=>'main menu', // your main menu
'dash_nav'=>'dashboard menu', //your dashboard menu
)
);
}?>
And then create a page template for dashboard which will have this:
<?php wp_nav_menu(array('menu'=>'dashboard menu'));?>
EDIT:
Well you could edit the header.php and add something like this
<?php if (is_page_template('dashboard.php') :?>
<link href="csspath" rel="stylesheet" type="text/css" />
<?php endif;?>
That way you add another css file that overrides the submenu.

Answer 2

I think I had a similar desire as you to select and only show a sub menu being just the children menu items from an existing wordpress menu. This can be done by editing the functions.php and adding a shortcode that has it's own walker class to target and display a submenu.
PHP code for "menu" shortcode and customized menu walker class (all goes in functions.php):
//register menu shortcode
add_shortcode('menu', 'shortcode_menu');
function shortcode_menu($args ) {
//don't echo the ouput so we can return it
$args['echo']=false;
//in case menu isn't found display a message
$args['fallback_cb']='shortcode_menu_fallback';
//check if showing a submenu, if so make sure everything is setup to do so
if (isset($args['show_submenu']) && !empty($args['show_submenu'])) {
if (!isset($args['depth'])) {
$args['depth']=1;
}
$args['walker']=new Sub_Menu_Walker_Nav_Menu();
}
$menu=wp_nav_menu( $args );
return $menu;
}
//message to display if menu isn't found
function shortcode_menu_fallback($args ) {return 'No menu selected.';}
//special walker_nav_menu class to only display submenu
//depth must be greater than 0
//show_submenu specifies submenu to display
class Sub_Menu_Walker_Nav_Menu extends Walker_Nav_Menu {
function display_element( $element, &$children_elements, $max_depth, $depth=0, $args, &$output ) {
if ( !$element )
return;
$id_field = $this->db_fields['id'];
$displaythiselement=$depth!=0;
if ($displaythiselement) {
//display this element
if ( is_array( $args[0] ) )
$args[0]['has_children'] = ! empty( $children_elements[$element->$id_field] );
$cb_args = array_merge( array(&$output, $element, $depth), $args);
call_user_func_array(array(&$this, 'start_el'), $cb_args);
}
$id = $element->$id_field;
if ( is_array( $args[0] ) ){
$show_submenu=$args[0]['show_submenu'];
}else
$show_submenu=$args[0]->show_submenu;
// descend only when the depth is right and there are childrens for this element
if ( ($max_depth == 0 || $max_depth >= $depth+1 ) && isset( $children_elements[$id]) && $element->title==$show_submenu) {
foreach( $children_elements[ $id ] as $child ){
if ( !isset($newlevel) ) {
$newlevel = true;
//start the child delimiter
$cb_args = array_merge( array(&$output, $depth), $args);
call_user_func_array(array(&$this, 'start_lvl'), $cb_args);
}
$this->display_element( $child, $children_elements, $max_depth, $depth + 1, $args, $output );
}
unset( $children_elements[ $id ] );
}
if ( isset($newlevel) && $newlevel ){
//end the child delimiter
$cb_args = array_merge( array(&$output, $depth), $args);
call_user_func_array(array(&$this, 'end_lvl'), $cb_args);
}
if ($displaythiselement) {
//end this element
$cb_args = array_merge( array(&$output, $element, $depth), $args);
call_user_func_array(array(&$this, 'end_el'), $cb_args);
}
}
}
Display a submenu titled "About" from the "Main" menu (capitalization matters):
[menu menu='Main' show_submenu='About']
Display the full "Main" menu:
[menu menu='Main']
For further reading/reference see this wordpress question.

Answer 3

I am surprised that Wordpress doesn't have this option built into the wp_nav_menu function. It has always been a struggle to implement secondary or split menus in Wordpress. After trying a number of different solutions to accomplish this goal I finally decided to make my own plugin that lets you choose the start depth for your menu. So you can just set the start depth to '1' for a secondary menu.
you use the plugin like this:
wp_nav_plus(array('theme_location' => 'primary_navigation', 'start_depth' => 1));
The plugin is available on my site here for anyone interested: https://mattkeys.me/products/wp-nav-plus/