if ($comment['posted_by'] == $authUser['id']) {
    $data = $post->update([
        "comments.$key.description" => $dataArray['description'],
        "comments.$key.updated_at" => $dataArray['updated_at'],
    ]);
}

$post = Post::where('_id', $id)->where('comments.*.id', $commentId)->update(array('description' => $desc));

if ($subCommentId) {
    foreach ($comment as $nestedkey => $nestedComments) {
        if ($nestedComments['id'] === $subCommentId && $nestedComments['posted_by'] == $authUser['id']) {
            $data = $post->update([
                "comments.$key.$nestedkey.description" => $dataArray['description'],
                "comments.$key.$nestedkey.updated_at" => $dataArray['updated_at'],
            ]);
        }
    }
}

$post = Post::where('_id', $id)->where('comments.*.id', $commentId)->where('comments.*.*.id', $subCommentId)->update(array('description' => $desc));