- var_dump: documentation ( source)
<?php
$x = new DOMDocument('1.0', 'UTF-8');
$x->loadHTML('<html><head></head><body><p>fi</p><p>fai</p><p>foe</p><p>fum</p></body></html>');
$e = $x->getElementsByTagName('p')->item(0);
$y = new DOMDocument('1.0', 'UTF-8');
$y->appendChild($y->importNode($e, true));
var_dump($y->saveHTML());