使用url行从txt获取文件大小

Question

我想知道如何从txt中的url行获取文件大小，然后将获取的文件大小返回到单个txt。我找到了这段代码，但我没有设法将所有大小输出到一个txt文件中。

function getRemoteFilesize($url, $formatSize = true)
{
    $head = array_change_key_case(get_headers($url, 1));
    // content-length of download (in bytes), read from Content-Length: field
    $clen = isset($head['content-length']) ? $head['content-length'] : 0;
    // cannot retrieve file size, return "-1"
    if (!$clen) {
        return -1;
    }
    if (!$formatSize) {
        return $clen; // return size in bytes
    }
    $size = $clen;
    switch ($clen) {
        case $clen < 1024:
            $size = $clen .' B'; break;
        case $clen < 1048576:
            $size = round($clen / 1024, 2) .' KiB'; break;
        case $clen < 1073741824:
            $size = round($clen / 1048576, 2) . ' MiB'; break;
        case $clen < 1099511627776:
            $size = round($clen / 1073741824, 2) . ' GiB'; break;
    }
    return $size; // return formatted size
}
$url = 'url_here';
echo getRemoteFilesize($url); // echoes "7.51 MiB"