It's a property on DOMElement
called tagName
. E.g.:
<?php
$xml = <<<XML
<alist>
<a>
<a1>text a</a1>
<a2>text a</a2>
</a>
<b>
<b1>text b</b1>
<b2>text b</b2>
</b>
</alist>
XML;
$dom = new DOMDocument();
$dom->loadXML($xml);
$alist = $dom->getElementsByTagName('alist')->item(0);
foreach($alist->childNodes as $child) {
if ($child->nodeType === XML_ELEMENT_NODE) var_dump($child->tagName);
}