ul li tree generator function

ulLiTree.php

<?php
$tree = array(
  'Parent' => array(
    'Children 1' => array(
      '1\'s Child 1',
      '1\'s Child 2',
      '1\'s Child 3'
     ),
     'Children 2' => array(
     	'2\'s Child 1',
     	'2\'s Child 2',
     	'2\'s Child 3'
     )
   )
 );

function ulLiTree($tree) {
    $out = '<ul>';
    
    foreach($tree as $key => $value) {
		$out.= '<li>';
        if (is_array($value)) {
            $out.='<a href="#">'.$key.'</a>'.ulLiTree($value);
        } else {
            $out.= '<a href="#">'.$value.'</a>';
        }
        $out.= '</li>';
    }
    $out.= '</ul>';
    return $out;
}

echo ulLiTree($tree);

?>