How do I add the tertiary level from the main menu to my skin?

Question

Let's say I have the following menu:

• Smartphones
  • Android
    • LG Nexus 4
    • Samsung Galaxy Note 2
    • HTC One
    • Motorola Droid RAZR MAXX HD
  • iOS
    • iPhone 4
    • iPhone 4S
    • iPhone 5
  • Windows Phone
    • HTC Windows Phone 8X
    • HTC Windows Phone 8S
    • Nokia Lumia 920
    • Nokia Lumia 820

I want a menu that will display all the third level items if I'm on the parent node. So, if I'm on the Android page, I should see LG Nexus 4, Samsung Galaxy Note 2, HTC One, and Motorola Droid RAZR MAXX HD.

The only recommendation I keep seeing is to use the Menu block module, but I want to just create the menu myself in PHP. How?

Answer 1

I figured it out. In template.php, I added the following function:

function MYTHEME_preprocess_page(&$variables) {
    $active_tree = menu_get_active_trail();
    $parent = array_pop($active_tree);
    if($parent['depth'] == 3) {
        $parent = array_pop($active_tree);
    }

    $parameters = array(
        'active_trail' => array($parent['plid']),
        'only_active_trail' => FALSE,
        'min_depth' => 3,
        'max_depth' => 3,
        'conditions' => array('plid' => $parent['mlid']),
      );

    $tertiary_menu = menu_build_tree($parent['menu_name'], $parameters);

    $links = array();
    foreach($tertiary_menu as $branch=>$link) {
        array_push($links, $link['link']);
    }

    $tertiary_links_vars = array(
        'links' => $links,
        'attributes' => array('class' => array('sub-nav')),
        'heading' => array(
            'text' => t('Tertiary menu'),
            'level' => 'h2',
            'class' => array('element-invisible'),
        ),
    );

    $variables['tertiary_menu'] = theme_links($tertiary_links_vars);
}

In my page.tpl.php file, I added the following:

<?php print $tertiary_menu; ?>

Answer 2

I follow cowgod in his solution, although I propose a slight tweak which allows a more flexibel rendering of the menu in the template:

function MYTHEME_preprocess_page(&$variables) {
    $active_tree = menu_get_active_trail();
    $parent = array_pop($active_tree);
    if($parent['depth'] == 3) {
        $parent = array_pop($active_tree);
    }

    $parameters = array(
        'active_trail' => array($parent['plid']),
        'only_active_trail' => FALSE,
        'min_depth' => 3,
        'max_depth' => 3,
        'conditions' => array('plid' => $parent['mlid']),
      );

    $tertiary_menu = menu_build_tree($parent['menu_name'], $parameters);

    $links = array();
    foreach($tertiary_menu as $branch=>$link) {
        array_push($links, $link['link']);
    }

    $variables['tertiary_menu'] = $links;
}

In page.tpl.php , you can then add:

<?php 
    print theme('links', array(
      'links' => $tertiary_menu,
      'attributes' => array('class' => array('sub-nav')),
      'heading' => array(
        'text' => t('Tertiary menu'),
        'level' => 'h2',
        'class' => array('element-invisible'),
      ),
    ); 
?>

This way, you'll have a more flexible solution.