DOMDocument を使用して PHP の特定のクラスを持つ要素からテキストを抽出する方法

<p class="Heading1-P">
    <span class="Heading1-H">Chapter 1</span>
</p>
<p class="Normal-P">
    <span class="Normal-H">This is chapter 1</span>
</p>

$heading = ['Chapter 1', 'Chapter 2', 'Chapter 3'];
$content = ['This is chapter 1', 'This is chapter 2', 'This is chapter 3'];

// Load HTML into DOMDocument
$dom = new DOMDocument();
$dom->loadHTML($html);

// Create DOMXPath object
$xpath = new DOMXPath($dom);

// Get elements with desired class using XPath
$xpathQuery = "//*[@class='$class']";
$elements = $xpath->query($xpathQuery);

// Extract text from elements and store in arrays
$headings = [];
$contents = [];
foreach ($elements as $element) {
    $nodes = $element->childNodes;
    foreach ($nodes as $node) {
        $headings[] = $node->nodeValue;
    }
}

var_dump($headings);