PHPでXMLを配列にする方法 XML_Unserializer

<?php
include ('XML/Unserializer.php');

$xml = <<<XML
<video_list>
    <video>
	<author>youtuberocks</author>
	<id>k0gEeue2sLk</id> <!-- this ID can be used with youtube.videos.get_details -->
	<title>My First Motion Picture</title>
	<length_seconds>16</length_seconds> <!-- length of video -->
	<rating_avg>3.75</rating_avg>
	<rating_count>10</rating_count>
	<description>This is the video description shown on the YouTube site.</description>
	<view_count>170</view_count>
	<upload_time>1121398533</upload_time> <!-- UNIX-style time, seconds since 1/1/1970 -->
	<comment_count>1</comment_count> <!-- number of comments this video has -->
	<tags>feature film documentary</tags>
	<url>http://www.youtube.com/watch?v=k04Eeue24Lk</url>
	<thumbnail_url>http://static.youtube.com/get_still?video_id=k04Eeue24Lk</thumbnail_url>
	<embed_status>ok</embed_status>
    </video>
</video_list>
XML;

$unserializer = &new XML_Unserializer();
$unserializer->unserialize($xml);
$data = $unserializer->getUnserializedData();

print_r ($data);
?>

Array
(
    [video] => Array
	(
	    [author] => youtuberocks
	    [id] => k0gEeue2sLk
	    [title] => My First Motion Picture
	    [length_seconds] => 16
	    [rating_avg] => 3.75
	    [rating_count] => 10
	    [description] => This is the video description shown on the YouTube site.
	    [view_count] => 170
	    [upload_time] => 1121398533
	    [comment_count] => 1
	    [tags] => feature film documentary
	    [url] => http://www.youtube.com/watch?v=k04Eeue24Lk
	    [thumbnail_url] => http://static.youtube.com/get_still?video_id=k04Eeue24Lk
	    [embed_status] => ok
	)

)