подскажите как мне сделать подменю

<?php
/*
Written by: Adam Crownoble
Created: 5/8/2005
Updated: 8/6/2005 (Added Show in Menu support)
Email: [email protected]
Website: obledesign.com
Name: CascadingMenu
Description: Incorporates breadcrumbs into a menu.
Properties: &doc_id=Current Document ID;int;0 &parent_class=Parent CSS Class;string;parent &children_class=Children CSS Class;string;children &child_class=Child CSS Class;string;child &current_class=Current CSS Class;string;current
Thanks: to php.net for inspiration.
*/

// PSUEDO CONSTANTS //
$page_fields = 'id, pagetitle, menutitle, description, published, deleted, isfolder, hidemenu';

// INITIALIZE VARIABLES //
$end_tag = '';
$count = 1;
$parents = array();
$parents_html = '';
$children_html = '';
if(!$doc_id) { $doc_id = $modx->documentIdentifier; } // If doc_id not set use the current doc
$page = $modx->getPageInfo($doc_id,0,$page_fields);

// If the current page is a folder add it to the parent array
if($page['isfolder']) {
 $parents[$page['id']] = $page;
}

// Loop through each parent to the current page
// if it's published, not deleted and show in menu is set, add it to the parent array
while($page = $modx->getParent($page['id'],0,$page_fields)) {
 if($page['published'] && !$page['deleted'] && !$page['hidemenu']) {
  $parents[] = $page;
 }
}

// Reverse the array of parents so we can start at the top instead of the bottom
$parents = array_reverse($parents,true);

// Remove any unpublished, deleted or hidden parents
foreach($parents as $key=>$parent) {
 if(!$parent['published'] || $parent['deleted'] || $parent['hidemenu']) {
  unset($parents[$key]);
 }
}

$parent_count = count($parents);

// Loop through each parent and add it to the html
foreach($parents as $parent) {

 $id = $parent['id'];
 $title = ($parent['menutitle'] ? $parent['menutitle'] : $parent['pagetitle']);

 // Get classes
 $parent_classes = " {$parent_class} ";
 if($parent['id'] == $doc_id) { $parent_classes .= " $current_class "; }
 if($count==$parent_count) { $parent_classes .= " {$children_class} "; }

 // End the <li> tag immpediatley only if this isn't the current parent because it's children need to go inside the <li> 
 $end_tag = ($count<$parent_count ? "</li>\n" : "\n");

$parents_html .= <<<EOD
<li><a href="[~{$id}~]">{$title}</a>{$end_tag}
EOD;

 $count++;

}

// Get the children of the last parent
$children = $modx->getActiveChildren($parent['id']);

// Loop through each child and add it to the html
foreach($children as $child) {

 // Get title
 $title = $child['menutitle'] ? $child['menutitle'] : $child['pagetitle'];

 // Get classes
 $child_classes = " {$child_class} ";
 if($child['id'] == $doc_id) {
  $child_classes .= " {$current_class} ";
 }

$children_html .= <<<EOD
<li><a href="[~{$child['id']}~]">{$title}</a></li>\n
EOD;

}

// Complile the HTML into one HTML string
$html = <<<EOD
  <ul>
   {$children_html}
  </ul>
EOD;

// If there are parents...
if($parents_html)
{
$html = <<<EOD
<ul>
  {$children_html}
</ul>
EOD;
}

// Return the HTML
return $html;
?>