<?
$string = <<<XML
<xml>
  <body1>
    <div><h1>Hello World</h1></div>
  </body1>
  <body2>
    <div><h2>Goodby Moon</h2></div>
  </body2>
</xml>
XML;

$xml = simplexml_load_string($string);
echo $xml->body1->div->asXML();

<div><h1>Hello World</h1></div>