PHP: How to know if a user is currently downloading a file? - php

Question

I'm developing a quick rapidshare-like site where the user can download files. First, I created a quick test setting headers and using readfile() but then I found in the comments section there's a way to limit the speed of the download, which is great, here's the code:
$local_file = 'file.zip';
$download_file = 'name.zip';
// set the download rate limit (=> 20,5 kb/s)
$download_rate = 20.5;
if(file_exists($local_file) && is_file($local_file))
{
header('Cache-control: private');
header('Content-Type: application/octet-stream');
header('Content-Length: '.filesize($local_file));
header('Content-Disposition: filename='.$download_file);
flush();
$file = fopen($local_file, "r");
while(!feof($file))
{
// send the current file part to the browser
print fread($file, round($download_rate * 1024));
// flush the content to the browser
flush();
// sleep one second
sleep(1);
}
fclose($file);}
else {
die('Error: The file '.$local_file.' does not exist!');
}
But now my question is, how to limit the number of downloads at the same time? How can I check there's still a connection with some user's IP?
Thanks.

Answer 1

Does a user have a login? if not just use sessions, or even better track on their ip-address.
Here's a sessions example:
$_SESSION['file_downloading']==true;
$file = fopen($local_file, "r");
while(!feof($file))
{
// send the current file part to the browser
print fread($file, round($download_rate * 1024));
// flush the content to the browser
flush();
// sleep one second
sleep(1);
}
$_SESSION['file_downloading']=null;
fclose($file);}
Then above all this code,
if(!empty($_SESSION['file_downloading']))
//perform a redirect or reduce their download rate or something.
Next option is via ip address.
//http://wiki.jumba.com.au/wiki/PHP_Get_user_IP_Address
function VisitorIP()
{
if(isset($_SERVER['HTTP_X_FORWARDED_FOR']))
$TheIp=$_SERVER['HTTP_X_FORWARDED_FOR'];
else $TheIp=$_SERVER['REMOTE_ADDR'];
return trim($TheIp);
}
get the visitor ip address, store this in the database along with the datetime stamp. Then simply remove that ip address when the file is finished downloading. Are you using a database system?