请问一个XML有关问题

192.168.1.1
192.168.1.2 
192.168.1.3 
192.168.1.4
192.168.1.5


192.168.1.11
192.168.1.12
192.168.1.13
192.168.1.14
192.168.1.15


192.168.1.21
192.168.1.22
192.168.1.23
192.168.1.24
192.168.1.25


EOF;

$dom = new DOMDocument();
$ret = $dom->loadXML($xml, LIBXML_NOBLANKS);
$xpath = new DOMXpath($dom);
$node_list = $xpath->query('/user/username[@name="admin"]/iplist');
for ($i = 0; $i != $node_list->length; ++ $i) {
        echo $node_list->item($i)->nodeValue . PHP_EOL;
}
?>

------解决方案--------------------
PHP code
$s =<<< XML



192.168.1.1
192.168.1.2
192.168.1.3
192.168.1.4
192.168.1.5


192.168.1.11
192.168.1.12
192.168.1.13
192.168.1.14
192.168.1.15


192.168.1.21
192.168.1.22
192.168.1.23
192.168.1.24
192.168.1.25


XML;

$dom = new domDocument;
$dom->loadXML($s);
$xpath = new DOMXPath($dom);

//使用xpath定位修改
$p = $xpath->query("//username[@name='admin']/iplist[.='192.168.1.1']")->item(0);
$p->nodeValue = 'abcd';

//使用xpath定位删除
$p = $xpath->query("//username[@name='admin']/iplist[.='192.168.1.2']")->item(0);
$p->parentNode->removeChild($p);

echo $dom->saveXML();