WordPress List Subpages Even if On Subpage

I'm building a new site and the navigation on it requires me to use a different bit of code for parent and child pages. I thought I'd share the code for those out there building a similar navigation. Here's a handy bit of code that you can use to display all subpages on a subpage. For instance, you have your pages setup like so:

Page: Fruit
subpage: Banana
subpage: Apply
subpage: Orange

On Parent Page

If you were wanting to show a navigation menu of all subpages in the Fruit category you could use the following bit of code:

<?php
  $children = wp_list_pages('title_li=&child_of='.$post->ID.'&echo=0');
  if ($children) { ?>
  <ul id="mainNav">
	<div id="locationsNavHead">choose a product</div>
  <?php echo $children; ?>
  </ul>
<?php } ?>

On Subpages

For child, or subpages, we could use the following bit of code:

<div id="sidebar">
<?php
//list subpages even if on a subpage
  if($post->post_parent)
  $children = wp_list_pages("title_li=&child_of=".$post->post_parent."&echo=0");
  else
  $children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0");
  if ($children) { ?>
  <ul id="mainNav">
  <div id="locationsNavHead">choose a product</div>
  <?php echo $children; ?>
  </ul>
<?php } ?>
</div>

If you are confused at what this all means please comment below and check out wp_list_pages() over at the WordPress Codex

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