<?php

$html = '<div class="content"><div>Content</div></div>';

$dom = new DOMDocument('1.0', 'UTF-8');
$dom->loadHTML($html, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);

$xpath = new DOMXPath($dom);
$divs = $xpath->query('//div[@class="content"]');

foreach($divs as $div) { 
	
   foreach ($div->childNodes as $childNode) {
       echo $dom->saveHTML($childNode);
   }
}
