php写xml文件,问题奇怪!!请高手帮忙!!!

Question

<?xml version="1.0" encoding="GB2312"?>
<titleProgramInfo>
<titles>
<title code="06122500030000000" name="" status="add"/>
<title code="06122500020000000" name="" status="add"/>
</titles>
<programs>
<program code="06122500030010000" name=""status="add"price="200"/>
<program code="06122500030020000" name="" status="add" price="200"/>
<program code="06122500010000000" name="" status="add" price="100"/>
<program code="06122500020010000" name="" status="add" price="200"/>
<program code="06122500020020000" name="" status="add" 200="200"/>
</programs><relations>
<relation titleCode="06122500030000000"/>
<relation titleCode="06122500020000000"/>
</relations></titleProgramInfo>
我用XPATH查到节点,relation titleCode="06122500030000000"然后再往其下面加入新的值<list programCode="" status=""></list><?php
$dom = new DomDocument();
//然后载入XML文件
$dom ->load("titleProgramInfo.xml");
$xpath = new domxpath($dom);
$item = $xpath->query("/titleProgramInfo/relations/relation[@titleCode = '06110700020000000']");//->item(0)->getAttribute('titleCode');//echo $item; $list=$dom->createElement('list');
$list->setAttribute("programCode","ttttttttt");
$list->setAttribute("status","456525");
    $item->item(0)->appendChild($list);
    $inl=$dom->getElementsByTagName('relation')->item(0);
$inl->insertBefore($list);
$dom->save('titleProgramInfo.xml');
?>