parent-child wordpress pages

<?php
	$parent = $post->ID;
	while($parent)
	{
		$theParent = $parent;
		$parentPost = get_post($parent);
		$parent = $parentPost->post_parent;
	}
	$args=array('child_of' => $theParent);
	$pages = get_pages($args);
	foreach($pages as $key=> $value)
	{
		$allpages .=$value->ID.",";
	}



	$pages = get_pages('parent=0');
	foreach($pages as $key=>$value)
	{
		$allpages.=$value->ID.",";
	}
	$allpages = substr_replace($allpages ,"",-1);

	if ($allpages) { ?>
  		<ul>
  			<?php wp_list_pages("title_li=&include=".$allpages); ?>
  		</ul>
  	<?php }
		else
		{
		?>
		<ul>
		<?php 		wp_list_pages("title_li=&depth=1");?>
		</ul>
		<?php }
   ?>