如何安全地检查节点是否为空？(Symfony 2 Crawler)

use Symfony\Component\DomCrawler\Crawler;

$html = '<div class="content">
    <p>Hello, World!</p>
    <p></p>
</div>';

$crawler = new Crawler($html);

// 获取所有的p标签
$pTags = $crawler->filter('p');

foreach ($pTags as $i => $pTag) {
    $crawlerNode = new Crawler($pTag);
    $text = $crawlerNode->text();

    if (empty(trim($text))) {
        echo "节点 {$i} 为空。\n";
    } else {
        echo "节点 {$i} 不为空。\n";
    }
}