Displaying large PDF files using PHP headers - php

Question

I took the following piece of code from github
function smartReadFile($location, $filename, $mimeType = 'application/pdf')
{
if (!file_exists($location))
{
header ("HTTP/1.1 404 Not Found");
return;
}
$size = filesize($location);
$time = date('r', filemtime($location));
$fm = #fopen($location, 'rb');
if (!$fm)
{
header ("HTTP/1.1 505 Internal server error");
return;
}
$begin = 0;
$end = $size - 1;
if (isset($_SERVER['HTTP_RANGE']))
{
if (preg_match('/bytes=\h*(\d+)-(\d*)[\D.*]?/i', $_SERVER['HTTP_RANGE'], $matches))
{
$begin = intval($matches[1]);
if (!empty($matches[2]))
{
$end = intval($matches[2]);
}
}
}
if (isset($_SERVER['HTTP_RANGE']))
{
header('HTTP/1.1 206 Partial Content');
}
else
{
header('HTTP/1.1 200 OK');
}
header("Content-Type: $mimeType");
header('Cache-Control: public, must-revalidate, max-age=0');
header('Pragma: no-cache');
header('Accept-Ranges: bytes');
header('Content-Length:' . (($end - $begin) + 1));
if (isset($_SERVER['HTTP_RANGE']))
{
header("Content-Range: bytes $begin-$end/$size");
}
header("Content-Disposition: inline; filename=$filename");
header("Content-Transfer-Encoding: binary");
header("Last-Modified: $time");
$cur = $begin;
fseek($fm, $begin, 0);
while(!feof($fm) && $cur <= $end && (connection_status() == 0))
{
print fread($fm, min(1024 * 16, ($end - $cur) + 1));
$cur += 1024 * 16;
}
}
It is working for smaller files. But in case of large files it isn't working properly. I tried with a 100MB file. The PDF is partially loaded that too with a black background. I don't know what's wrong in the code. I suspect I had to modify the headers, but I don't know what to add/replace. I have tried many alternatives given in many sites, but none of them worked.
Thank you for any help