Bandwidth & Hotlinking

I offer a free file upload and storage server. I'm thinking of coding the script in Coldfusion, but need to know how to actually calculate the amount of bandwidth used for each individual image. This information will be available in the administrator page.

Also, I want to allow hotlinking, but I don't want people to link directly to the .jpg file. Instead, I want them to link to a CFM file and still be able to use that link in their <img> tags. Is there a way to achieve this?

Any advice would be appreciated, thanks.
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enuneConnect With a Mentor Commented:
Hi lifegauge,

Theoretically, you should be able to calculate the amount of bandwidth used by simply retrieving the size of the file/image via PHP's filesize() function, and multiplying it by the amount of times the file has been downloaded.

As for your second question, it is quite simple to achieve what you want. I use the following code to read files and send them to users from my file-archive:

        header("Pragma: ");
        header("Cache-Control: ");
        header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
        header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
        header("Cache-Control: no-store, no-cache, must-revalidate");  //HTTP/1.1
        header("Cache-Control: post-check=0, pre-check=0", false);
        header("Content-length: {$fd[file_size]}" );
        header("Content-type: {$fd[file_type]}" );
        header("Content-disposition: attachment; filename={$fd[file_filename]}");

where '$fd' is an array containing
a) The size of the file
b) the MIME type (file_type)
c) the file name (file_filename)
d) the directory and real filename on my server (file_dir and file_filename)

You can then point the user to a link such as:
and, using the id number, retrieve the file record from your database that they request, and using readfile(), send them the data.

Hope this helps.

virmaiorConnect With a Mentor Commented:
if you have total control of the webserver and its apache, then you can let them hotlink with .jpg extension by using a combination of php and .htaccess


ReWriteEngine On
ReWriteRule . /imageserver.php


if ($_SESSION['usergroups'][0] == 'y') //check if you login to download the file

        $file = $_SERVER["DOCUMENT_ROOT"] . $_SERVER["REQUEST_URI"];
        if (file_exists($file))
              //header("Content-type: application/force-download");
              header("Content-Transfer-Encoding: Binary");
              header("Content-length: ".filesize($file));
              header("Content-disposition: attachment; filename=".basename($file). "");
                  include "error.php";
       include "error.php";


by combining these two files with a DB backend that checks bandwidth usage, you can let them hotlink to the ".jpg" (which means they end up calling the php script that checks and then sends the real .jpg if they can get it)
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