DOM-based Solution

Harnessing the power of Document Object Model (DOM), you can devise a surgical excision of the targeted section. This approach permits comprehensive manipulation of HTML structures.

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();
?>

In the provided code snippet, we first load the HTML string into a DOMDocument instance. Subsequently, we employ a DOMXPath object to pinpoint the element with the designated id attribute. If the element exists, we eliminate it and its descendants using the removeChild() method. The processed HTML is then extracted and displayed.