Show siblings (if any) and parents

Question

My question relates to showing the parents and siblings of the current page.

If I am on level 2 page, I would like to show siblings without their children. If I am on level 3 page, I would like to show siblings, parent and parent's siblings.

For example if I would have page levels like this:

Animals (level 1)
- Fish (level 2)
-- Salmon (level 3)
-- Trout
-- Pike
- Mammals
-- Dogs
-- Cats
Plants

If I am on the page Fish, I would like to show siblings:

Fish
Mammals

If I am on the page Salmon, I would like to show siblings, parent and parents siblings:

Fish
- Salmon
- Trout
- Pike
Mammals

My current code looks like this:

<?php
if($post->post_parent)
$children = wp_list_pages("title_li=&child_of=".$post->post_parent."&echo=0&sort_column=menu_order");
else $children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0&sort_column=menu_order");
if ($children) { ?>
<ul><?php echo $children; ?></ul>
<?php } ?>

Answer 1

As it stands your code almost works, but it checks to see if the current page has a parent, which will always be true for both 2nd and 3rd level pages.

WordPress gives us get_ancestors to retrieve an ordered array of ancestors for any hierarchical object type:

get_ancestors( $object_id, $object_type );

So we can use get_ancestors( $post->ID, 'page' ) and count the elements to help us get the depth right for your navigation.

if($post->post_parent) {

    $ancestors = get_ancestors( $post->ID, 'page' );

    if ( 1 == count( $ancestors ) ) {

            echo '<ul>';

            wp_list_pages(
                array (
                    'title_li' => '',
                    'sort_column' => 'menu_order',
                    'child_of' => $ancestors[0],
                    'depth' => 1
                ) 
            );

            echo '</ul>';

    }

    if ( 2 == count( $ancestors ) ) {

            echo '<ul>';

            wp_list_pages(
                array (
                    'title_li' => '',
                    'sort_column' => 'menu_order',
                    'child_of' => $ancestors[1],
                    'depth' => 2
                ) 
            );

            echo '</ul>';

    }


}

You could be more clever with the logic, popping the last element off the ancestor array for example, but I've kept it verbose for clarity.