DOMDocumentExtended
Extension of DOMDocument class.
innerHTML() method exapmle usage.
<?php
require_once './DOMDocumentExtended.php';
use DOMDocumentExtended;
$html = "<p><strong>Exapmle</strong></p><p>HTML</p>";
$dom = new DOMDocumentExtended;
$dom->loadHTML($html);
$node = $dom->getElementsByTagName('body')[0];
$innerHTML = $dom->innerHTML($node);
echo '<pre>'.htmlentities($innerHTML).'</pre>';