Wordpress flat list

get_pages_flattened_tree.php

<?php
function get_pages_flattened_tree(&$flattened_list, $parent_id=0, $level=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['level'] = $level;
			$flattened_list[] = $holder;
			get_pages_flattened_tree($flattened_list, $page->ID, $level+1); // Call function recursively
			
		}
	}
}
$flattened_list = array();
get_pages_flattened_tree($flattened_list);
var_dump($flattened_list);