<?php
if(!$post->post_parent){
// will display the subpages of this top level page
$children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0");
}else{
// diplays only the subpages of parent level
//$children = wp_list_pages("title_li=&child_of=".$post->post_parent."&echo=0");
if($post->ancestors)
{
// now you can get the the top ID of this page
// wp is putting the ids DESC, thats why the top level ID is the last one
$ancestors = end($post->ancestors);
$children = wp_list_pages("title_li=&child_of=".$ancestors."&echo=0");
// you will always get the whole subpages list
}
}
if ($children) { ?>
<ul>
<?php
$parent_link = get_permalink($post->post_parent);
$parent_title = get_the_title($post->post_parent);
if ($post->post_parent) {
echo "<li><a href='".$parent_link."'>".$parent_title."</a></li>";
} else {
echo "<li class='current_page_item'><a href='".$parent_link."'>".$parent_title."</a></li>";
}
?>
<?php echo $children; ?>
</ul>
<?php } ?>