PHP Download file, limit max speed and calculate downloading speed - php

Question

I have written a script that gives you ability to download the file with my maximum file speed that I allow, however when I allow 'unlimited' speed like 10000kB/s then the ftell works strange, it behaves like it downloads with 10000kBps speed, which is not true and I can not make calculations in database like time remaining, current download speed and so on...
So browser downloads file after some time, but in database it is already like 'downloaded', how could I make some precision calculations even I set the unlimited speed so user can download a file at the speed of the network and the database values are also counted by his network speed not by the ftell(); which depends on $download_rate; ...?
Thanks in advance!
<?php
while(!feof($fopen)) {
//echo fread($fopen, 4096);
$this->get_allowed_speed_limit($download_rate);
//$download_rate = 350;
print fread($fopen, round($download_rate * 1024));
sleep(1); //needed for download speed limit
if(connection_status() != 0 || connection_aborted()) {
$bytes_transferred = ftell($fopen);
if($bytes_transferred < $bytes) {
//CANCELLED
$this->download_unsuccessfull($file_name);
} else {
//CANCELLED (but gets executed only on strange networks like eduroam in CZE)
$this->download_unsuccessfull($file_name);}
flush();
die;
} else {
$progress = ftell($fopen) / $bytes * 100;
if($progress >= 100) {
//DONE
$this->download_successfull($file_name);
flush();
} else {
//DOWNLOADING
if(ftell($fopen) != 0) {
$bytes_transferred = ftell($fopen);
$time_end = microtime(true);
$time = $time_end - $time_start;
$dl_speed = floor(($bytes_transferred / $time) / 1000);
///////HERE THE CALCULATIONS ARE TOTALLY WRONG, BECAUSE IT ALL DEPENDS ON THE INPUT OF $download_rate;
mysqli_query($con, "UPDATE `download_meter` SET `current_speed` = '".mysqli_real_escape_string($con, $bytes_transferred)."'");
$this->update_active_downloads($file_name, $bytes_transferred, $dl_speed);
}
flush();
}
}
//Activate this for delay download.
//flush();
//sleep(1);
}
?>

Answer 1

Limiting download speed is up to your webserver. PHP is too high level. It knows nothing of the outgoing data.
Apache: https://stackoverflow.com/a/13355834/247372
Nginx: http://www.nginxtips.com/how-to-limit-nginx-download-speed/
The same goes for measuring: the webserver will know and might tell you somehow. Logs, unix socket, after-the-fact, I don't know. Those links will know.

Answer 2

How about (re)adding that sleep(1); thing to the WHILE loop? From what I can see the script outputs the file almost all at once (as fast as it can) and there's nothing that pauses it so it can actually limit the download speed.
That way you will know that each second you send just 64kbytes (or whatever) and even though you can't be sure that the user can in fact recieve this much data/second (whoa, so fast!), it could be a bit more precise than what you have in there now.
Or am I getting this wrong?