- iterator_to_array: documentation ( source)
<?php
$dom = new DOMDocument();
$dom->loadHtml('
<form>
<label>a</label>
<input />
<label>b</label>
<input />
<label>c</label>
<input />
</form>
', LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
$xpath = new DOMXPath($dom);
foreach ($xpath->query("//label") as $label) $label->parentNode->removeChild($label);
echo $dom->saveHTML();
//
$dom = new DOMDocument();
$dom->loadHtml('
<form>
<label>a</label>
<input />
<label>b</label>
<input />
<label>c</label>
<input />
</form>
', LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
foreach (iterator_to_array($dom->getElementsByTagName('label')) as $label) $label->parentNode->removeChild($label);
echo $dom->saveHTML();