【XML文件如下:】
<?xml version="1.0"?>
<online>
<userid time="2007-06-13 11:20:08" ip="127.0.0.1"/>
<userid time="2007-06-13 13:22:15" ip="localhost"/>
<userid time="2007-06-13 17:17:00" ip="localhost"/>
</online>
注:如要将“userid”节点的“ip”的值给修改了,请问用PHP怎么来实现?