php生成xml

<?php
$dom = new DOMDocument("1.0", 'utf8');
$dom->formatOutput = true;
header("Content-Type: text/plain");
$xmldir = dirname(__FILE__);
$user = $dom->createElement("user");
$dom->appendChild($user);
$user_data = array(
'userinfo' =>array(
   'username'=>'admin',
   'password'=>123456
),
'money'=>array(
   'left'=>1000,
   'totalprice'=>52000
)
);
foreach ($user_data as $k=>$v){
$node = $dom->createElement($k);
$user->appendChild($node);
$sub_node = '';
foreach ($v as $kk=>$vv){
   $sub_node = $dom->createElement($kk);
   $node->appendChild($sub_node);
   $sub_node->appendChild($dom->createTextNode($vv));
}
}
//$dom->save($xmldir.'\user.xml');
echo $dom->saveXML();
?>