Request:

http://demosite.frommers.biz/frommers/audience_interest_search.feed?audienceInterestId=530006&showChildren=true

Response:

<searchResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="feedschema/base.xsd" totalResultCount="1" currentPage="1" currentPageResultCount="1" totalPageCount="1">
  <audienceInterestResult id="530006" name="Events">
    <children>
      <audienceInterestResult id="141301" name="Arts"/>
      <audienceInterestResult id="141307" name="Classical Music"/>
      <audienceInterestResult id="141302" name="Festivals &amp; Heritage"/>
      <audienceInterestResult id="139861" name="Gay &amp; Lesbian"/>
      <audienceInterestResult id="140266" name="Kids &amp; Family"/>
      <audienceInterestResult id="141303" name="Lifestyle"/>
      <audienceInterestResult id="141304" name="Music &amp; Nightlife"/>
      <audienceInterestResult id="141306" name="Science &amp; Knowledge"/>
      <audienceInterestResult id="141305" name="Sport &amp; Outdoors"/>
      <audienceInterestResult id="140265" name="Weird &amp; Wonderful"/>
    </children>
  </audienceInterestResult>
</searchResponse>

Call the feed URL, using curl

$ch = curl_init(); // Set up curl
curl_setopt($ch, CURLOPT_URL, $url); // Add url
curl_setopt($ch, CURLOPT_HEADER, 0); // Remove header
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); // Return data
curl_setopt($ch, CURLOPT_TIMEOUT, 10); // Set timeout, 10s
$response = curl_exec($ch); // Call feed
curl_close($ch); // Close curl, free resources

Convert response to XML, use xpath to get the Audience interests tree

$audienceInterestResponse = new SimpleXMLElement($response); // Create xml object
$audienceInterestResults = $audienceInterestResponse->audienceInterestResult; //Use xpath to get list of audience interests

Build output dynamically by iterating the list

<div>
 <ul>
  <?php foreach ($audienceInterestResults as $audienceInterest ) { ?>
    <li><a href="#"><?php echo $audienceInterest["name"];?> </a>
      <?php if ($audienceInterest->children) {?>
	<ul>
	 <?php foreach ($audienceInterest->children->audienceInterestResult as $audienceInterestChild ) { ?>
	   <li><a href="#"><?php echo $audienceInterestChild["name"];?></a></li>
	 <?php } ?>
	</ul>
       <?php } ?>
   </li>
  <?php } ?>
  </ul>
</div>