Display Wordpress pages in a hierarchical order

functions.php

<?php
function getPagesInHierachy($post, $options = null) {
	// default args for wp_list_pages (show only top level pages)
	$args = array('depth' => 1);

	if(is_page()) {
		// get top level page ID from current page
		$parents = get_post_ancestors( $post->ID );
		$parent = ($parents) ? $parents[count($parents)-1]: $post->ID;

		if (get_pages('parent=0')) {
			$pageids = array();
			foreach (get_pages('parent=0') as $page) {
				$pageids[]= $page->ID;
				// check page is the same as the top level page of the current page
				if($page->ID == $parent) {

					$children = get_pages('child_of='.$parent);
					if($children) {
						foreach ($children as $child) {
							if($child->post_parent == $parent) {
								$pageids[]= $child->ID;
							}
							if( in_array($child->post_parent,$parents)) {
								$pageids[]= $child->ID;
							}
							if($child->post_parent == $post->ID) {
								$pageids[]= $child->ID;
							}
						}
					}
				}
			}

			$pageids = array_unique($pageids);

			// new args for wp_list_pages
			$args = array('include' =>	$parent . ',' . implode(",", $pageids));
		}
	}

	if (!empty($options)) $args = array_merge($args, $options);
	return $args;
}

gistfile1.txt

<?php 
// Default
wp_list_pages(getPagesInHierachy($post)); 

// List wp pages with parameters
wp_list_pages(getPagesInHierachy($post, array('title_li' => '')));

?>