It is amazingly simple to limit download speeds with php using no more than a half-handful of built in functions.

To get started, define the download path, filename, and download speed.

$file_path = "/path/to/file/demosong.mp3";
$file_name = "Cool_Song.mp3";
//download speed is in kb/s
$download_rate = 50;

note: you can easily change the download rate on a per-mimetype basis. ex:

if(strstr($file_name,'.mp3'))
{
$download_rate = 30;
}
else
{
$download_rate = 150;
}

Now, check that the file exists and then send some header information.

if(file_exists($file_path) && is_file($file_path))
{
header('Cache-control: private');
header('Content-Type: application/octet-stream');
header('Content-Length: '.filesize($file_path));
header('Content-Disposition: filename='.$file_name);
flush();

note: it is a good idea to leave the flush() in there.

All we have to do now is read the file in chunks. PHP will sleep every second and output the $download_rate to the browser.

$file = fopen($file_path, "r");
while(!feof($file)) {
print fread($file, round($download_rate * 1024));
flush();
sleep(1);
}
fclose($file);
}
else
{
die('Error: The file '.$file_name.' does not exist!');
}

That sums it up. Below is the file code.

$file_path = "/path/to/file/demosong.mp3";
$file_name = "Cool_Song.mp3";
//download speed is in kb/s
$download_rate = 50;
if(strstr($file_name,'.mp3'))
{
$download_rate = 30;
}
else
{
$download_rate = 150;
}
if(file_exists($file_path) && is_file($file_path))
{
header('Cache-control: private');
header('Content-Type: application/octet-stream');
header('Content-Length: '.filesize($file_path));
header('Content-Disposition: filename='.$file_name);
flush();
$file = fopen($file_path, "r");
while(!feof($file)) {
print fread($file, round($download_rate * 1024));
flush();
sleep(1);
}
fclose($file);
}
else
{
die('Error: The file '.$file_name.' does not exist!');
}