php修改和增加xml结点属性

<?xml version="1.0" encoding="UTF-8" ?>
<clientSet>
<server url="192.168.0.180" port="1935" />
<rootPath value="" />
<homePath value="http://www.aaa.com" />
<helpPath value="help.html" />
<language value="en" />
<theme value="default" />
<visibleMarquee value = "true" />
<visibleWhitePaper value="true" />
<showMemberRoomForGuest value = "true" />
<emotions enabled="true" column="5" autoPlay="false">
<item name="Birthday" src="cartoon/movie/birthday.swf" thumb="cartoon/preview/birthday-small.swf" duration="15"/>
<item name="Boom" src="cartoon/movie/boom.swf" thumb="cartoon/preview/boom-small.swf" duration="6"/>
<item name="Bubble" src="cartoon/movie/bubble.swf" thumb="cartoon/preview/bubble-small.swf" duration="7.5"/>
<item name="Cry" src="cartoon/movie/cry.swf" thumb="cartoon/preview/cry-small.swf" duration="5.4"/>
<item name="Doggie" src="cartoon/movie/doggie.swf" thumb="cartoon/preview/doggie-small.swf" duration="13"/>
<item name="Greeting" src="cartoon/movie/greeting.swf" thumb="cartoon/preview/greeting-small.swf" duration="7.4"/>
<item name="Football" src="cartoon/movie/football.swf" thumb="cartoon/preview/football-small.swf" duration="2.2"/>
</emotions >
</clientSet>

<?
$dom=new DOMDocument('1.0');
$dom->load('x.xml');
$em=$dom->getElementsByTagName('emotions');
$em=$em->item(0);
$items=$em->getElementsByTagName('item');
foreach($items as $a){
foreach($a->attributes as $b){
if($b->nodeValue=='Birthday'){
$a->setAttribute('name','nBirthday');
}
}
}
$t=$dom->createElement('item');
$t->setAttribute('name','x');
$t->setAttribute('src','www.sohu.com');
$t->setAttribute('duration','duration');
$em->appendChild($t);
$dom->save('x.xml');
?>