get_pages_tree.php

<?php
function get_pages_tree($parent_id=0){

    $args = array(
		'parent'=>$parent_id
	);
	
	$pages = get_pages( $args );

	if($pages){
		$list=array();
		foreach($pages as $page){
			$holder = (array) $page; // Cast as array
			$holder['children'] = get_pages_tree($page->ID); // Call function recursively
			$list[] = $holder;
		}
		return $list;
	}
	return array();
}

get_pages_tree();