添加子项时使用PHP进行XML文件样式设置

Question

I want to add style in an XML file with a PHP script.

Now I have this:

        $file = 'requests.xml';
        $xml = simplexml_load_file($file);
        $requests = $xml->request;
        $request = $requests->addChild('item');
        $request->addChild('artist', $_GET["artist"]);
        $request->addChild('title', $_GET["title"]);
        $request->addChild('status', 'In Progress');
        $xml->asXML($file);

When something gets inserted it comes out in the file like this:

<parent>
<item><artist>aaa</artist><title>aaaa</title></item><item><artist>aaa</artist><title>aaaa</title></item>
</parent>

But I want it to come out like this:

<parent>
    <item>
       <artist>aaa</artist>
       <title>aaaa</title>
     </item>
    <item>
       <artist>aaa</artist>
       <title>aaaa</title>
     </item>
</parent>

Hope someone can help me witht his.

Thanks in advance :)