how i can grab value and node as string using simplexml in php

example i have xml code like this:

$xml=<<<XML
<?xml version="1.0"?>
<cars>
  <desc1>
       <h1>Title 1</h1>
       <p>Content</p>
  </desc1>
  <desc2>
       <h1>Title 1</h1>
       <p>Content</p>
  </desc2> 
</cars>
XML;

how i can grab string between tag <desc1>...</desc1> using simplexml so the output like this:

$output='<h1>Title 1</h1>
           <p>Content</p>';

thanks in advance :)