Large files failing to download using readfile() - php

Question

I have the following code to force download an IPA file (after codesigning it with a script). It works fine with smaller files but with larger files, my web server starts returning a 500 Internal Server Error. Would someone be able to help me tweak my existing code to overcome this issue?
$time = md5(time());
// Runs code signing script here
// And then attempts to initiate download
$path = "done/$time/";
$latest_ctime = 0;
$latest_filename = '';
$d = dir($path);
while (false !== ($entry = $d->read())) {
$filepath = "{$path}/{$entry}";
if (is_file($filepath) && filectime($filepath) > $latest_ctime) {
$latest_ctime = filectime($filepath);
$latest_filename = $entry;
}
}
header("Cache-Control: public");
header("Content-Description: File Transfer");
header("Content-Disposition: attachment; filename=$time.ipa");
header("Content-Type: application/ipa");
header("Content-Transfer-Encoding: binary");
// Read the file from disk
readfile("done/$time/".$latest_filename);
// header('location: dashboard.php');
} else {
// Throwback
die("Failed. Contact support. // <p>$sign</p>");
}

Answer 1

Here is an example:
$filepath = "done/{$time}/{$latest_filename}";
$size = filesize($filepath);
$mimetype = 'application/ipa';
// Turn off buffering
if (ob_get_level()) {
ob_end_clean();
}
$handle = fopen($filepath, 'rb');
if ($handle !== false && $size > 0) {
#flock($handle, LOCK_SH);
$filename = rawurldecode($filepath);
$old_max_execution_time = ini_get('max_execution_time');
$old_cache_limiter = session_cache_limiter();
ini_set('max_execution_time', 0);
session_cache_limiter(false);
header("Cache-Control: public");
header("Content-Description: File Transfer");
header('Content-Type: ' . $mimetype);
header('Content-Transfer-Encoding: binary');
header('Content-disposition: attachment; filename="'. $filename .'"');
// or your variant
// header("Content-Disposition: attachment; filename=" . md5(time()));
header("Content-Length: $size");
$start = 0;
$end = $size - 1;
$chunk = 8 * 1024;
$requested = (float)$end - (float)$start + 1;
while (! $error) {
if ($chunk >= $requested) {
$chunk = (integer)$requested;
}
set_time_limit(0);
while (! feof($handle) && (connection_status() === 0)) {
if (! $buffer = #fread($handle, $chunk)) {
$error = true;
break 2;
}
print($buffer);
flush();
}
#flock($handle, LOCK_UN);
#fclose($handle);
ini_set('max_execution_time', $old_max_execution_time);
session_cache_limiter($old_cache_limiter);
break;
}
if ($error) {
// 500 - Internal server error
exit;
}
} else {
// Can't open file
exit;
}

Answer 2

Maybe problem in script time execution.
Try to set ini_set('max_execution_time', 0);
Also try to read and send file by chunks.