How to strip a tag and all of its inner html using the tag’s id?

With native DOM

$dom = new DOMDocument;
$dom->loadHTML($htmlString);
$xPath = new DOMXPath($dom);
$nodes = $xPath->query('//*[@id="anotherDiv"]');
if($nodes->item(0)) {
    $nodes->item(0)->parentNode->removeChild($nodes->item(0));
}
echo $dom->saveHTML();