PHP-Downloadscript - download limit doesn´t work - php

Question

when i use this phpcode to download a file with a downloadspeed of 300Kb/s i use this:
function readfile_chunked($dl_link, $filesize_file) {
$chunksize = 300*1024; #Buffersize in Byte
$data = '';
$handle = fopen($dl_link, 'rb');
while (!feof($handle)) {
$data = fread($handle, $chunksize);
sleep(1);
print $data;
#ob_flush();
#flush();
}
fclose($handle);
}
But it doesn´t work! :-(
When i start the Download, the speed is under one KB/s and it breaks and then resume, and so on.
When i take off this "sleep(1)" in the code above, then the download starts and all is good, but it runs with fullspeed. -> logical!
Why is this?

Answer 1

That looks mostly okay, however try the following:
function readfile_chunked($path, $speed)
{
if (is_file($path) !== true)
{
exit('not a local file');
}
header('Pragma: public');
header('Cache-Control: public, no-cache');
header('Content-Type: application/octet-stream');
header('Content-Length: ' . filesize($path));
header('Content-Disposition: attachment; filename="' . basename($path) . '"');
header('Content-Transfer-Encoding: binary');
$handle = fopen($path, 'rb');
while (!feof($handle))
{
echo fread($handle, $speed * 1024); sleep(1);
while (ob_get_level() > 0)
{
ob_end_flush();
}
flush();
}
fclose($handle);
}
readfile_chunked('/path/to/your/file.ext', 300);

Answer 2

You may want to try adding #ob_flush_end() at first to disable output buffering, and remove #ob_flush() in the loop. The delay may be because of the output buffering.
You may also try replacing print with echo. You may gain some performance improvement.
Also try a smaller chunk and use usleep instead for a shorter delay time.