function treeOut ($tree) {
$markup = "";
foreach ($tree as $branch => $twig) {
$markup .= '<li>'. ((is_array($twig)) ? $branch . treeOut($twig) : $twig) .'</li>';
}
return '<ul>' . $markup . '</ul>';
}
<?php
require 'functions/tree.php';
$tree = array('core' => array('init.php'), 'classes' => array('User.php', 'Hash.php', 'session.php'), 'functions' => array('security.php'), 'template' => array('index.template.php', 'includes' => array('header.template.php', 'footter.template.php')), 'index.php', 'login.php', 'register.php');
echo treeOut($tree);