php 异步获取文件下载文件大小（不用下载）

function getContentLength($strURL)
{
    $resURL = curl_init();
    curl_setopt($resURL, CURLOPT_URL, $strURL);
    curl_setopt($resURL, CURLOPT_PROGRESSFUNCTION, 'progressCallback');
    curl_setopt($resURL, CURLOPT_NOPROGRESS, false);
    curl_setopt($resURL, CURLOPT_RETURNTRANSFER, true);
    $res = curl_exec ($resURL);
    curl_close ($resURL);

}

function progressCallback($resource, $download_size = 0, $downloaded = 0, $upload_size = 0, $uploaded = 0)
{
    global $lens;
    if ($download_size > 0) {
        $res = curl_getinfo($resource);
        $url = $res['url'];
        $pkg = strstr($url,'?id=');
        $pkg = str_replace('?id=','',$pkg);
        $lens[$pkg] = $download_size;
        return $res;
    }

}