cURL의 헤더 전용 검색을 사용하여 원격 파일의 마지막 수정 날짜를 효율적으로 검색하는 방법은 무엇입니까?

curl_setopt($curl, CURLOPT_HEADER, true);
curl_setopt($curl, CURLOPT_NOBODY, true);

$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, "http://url/file.xml");
curl_setopt($curl, CURLOPT_HEADER, true);
curl_setopt($curl, CURLOPT_FILETIME, true);
curl_setopt($curl, CURLOPT_NOBODY, true);
curl_exec($curl);
$filetime = curl_getinfo($curl, CURLINFO_FILETIME); // Returns timestamp of last modification
curl_close($curl);

class URIInfo {
    public $info;
    public $header;
    private $url;

    public function __construct($url) {
        $this->url = $url;
        $this->setData();
    }

    public function setData() {
        $curl = curl_init();
        curl_setopt($curl, CURLOPT_URL, $this->url);
        curl_setopt($curl, CURLOPT_FILETIME, true);
        curl_setopt($curl, CURLOPT_NOBODY, true);
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($curl, CURLOPT_HEADER, true);
        $this->header = curl_exec($curl);
        $this->info = curl_getinfo($curl);
        curl_close($curl);
    }

    public function getFiletime() {
        return $this->info['filetime'];
    }

    // Other functions can be added to retrieve other information.
}

$uri_info = new URIInfo('http://example.com/index.html');
$filetime = $uri_info->getFiletime();
if ($filetime != -1) {
    echo date('Y-m-d H:i:s', $filetime);
} else {
    echo 'Filetime not available';
}