php readfile with limit bitrate

readfileLimit.php

<?php 

$file = $_SERVER['QUERY_STRING'];

header("Content-length: ".filesize($file));
header("Content-type: ".mime_content_type($file));

readfileLimit($file);

function readfileLimit($file, $limit='20k')
{
	$bsize = 1024;
	$f = popen("pv -B $bsize -L $limit '$file'",'r') or return false;
	while(!feof($f))
	{
		echo fread($f, $bsize);
		flush();
	}
	fclose($f);
}
?>