Remote file size without downloading file

Question

Is there a way to get the size of a remote file http://my_url/my_file.txt without downloading the file?

Answer 1

The simplest and most efficient implementation:

function remote_filesize($url, $fallback_to_download = false)
{
    static $regex = '/^Content-Length: *+\K\d++$/im';
    if (!$fp = @fopen($url, 'rb')) {
        return false;
    }
    if (isset($http_response_header) && preg_match($regex, implode("\n", $http_response_header), $matches)) {
        return (int)$matches[0];
    }
    if (!$fallback_to_download) {
        return false;
    }
    return strlen(stream_get_contents($fp));
}