如何使用PHP删除父元素？

I want to get the HTML inside the parent element using php. For example, I have this structure:

                   <p>
                      <p>this is my first xml file </p>
                  </p>

and I want to get below text as a result.

                  <p>this is my first xml file </p>

Make use of a DOM Parser

<?php
$html='<p>
                  <p>this is my first xml file </p>
              </p>';
$dom = new DOMDocument;
@$dom->loadHTML($html);
foreach ($dom->getElementsByTagName('p') as $tag){
    if(!empty($tag->nodeValue)){ echo $tag->nodeValue;}
    }