http force headers not working with above < 2GB files - php

Question

I have a script which is used to download large files in pdf and media format. I can't download it it gives http internal error sometimes it give 500 internal server error sometimes.
<?php
//The directory where the download files are kept - keep outside of the web document root
$strDownloadFolder = "uploads/";
//If you can download a file more than once
$boolAllowMultipleDownload = 0;
// 1. Create a database connection
//connect to the DB
$resDB = mysql_connect("localhost", "root", "");
mysql_select_db("downloader", $resDB);
if(!empty($_GET['key'])){
//check the DB for the key
$resCheck = mysql_query("SELECT * FROM downloads WHERE downloadkey = '".mysql_real_escape_string($_GET['key'])."' LIMIT 1");
if($resCheck == FALSE) { echo "QUERY FAILED: " . mysql_error(); }
$arrCheck = mysql_fetch_assoc($resCheck);
if(!empty($arrCheck['file'])){
//check that the download time hasnt expired
if($arrCheck['expires']>=time()){
if(!$arrCheck['downloads'] OR $boolAllowMultipleDownload){
//everything is hunky dory - check the file exists and then let the user download it
$strDownload = $strDownloadFolder.$arrCheck['file'];
if(file_exists($strDownload)){
//get the file content
$strFile = file_get_contents($strDownload);
//set the headers to force a download
header("Content-type: application/force-download");
header("Content-Disposition: attachment; filename=\"".str_replace(" ", "_", $arrCheck['file'])."\"");
//echo the file to the user
echo $strFile;
//update the DB to say this file has been downloaded
mysql_query("UPDATE downloads SET downloads = downloads + 1 WHERE downloadkey = '".mysqli_real_escape_string($_GET['key'])."' LIMIT 1");
exit;
}else{
echo "We couldn't find the file to download.";
}
}else{
//this file has already been downloaded and multiple downloads are not allowed
echo "This file has already been downloaded.";
}
}else{
//this download has passed its expiry date
echo "This download has expired.";
}
}else{
//the download key given didnt match anything in the DB
echo "No file was found to download.";
}
}else{
//No download key wa provided to this script
echo "No download key was provided. Please return to the previous page and try again.";
}
?>
Since http force headers are not working for larger files... I wanna use href with download attribute so when user clicks on it it should have direct encrypted link! with token or limited session!

Answer 1

file_get_contents reads the entire file into memory. If the file is larger than the available memory, it fails.
Instead you can read the file contents directly to the output stream:
//read whole file into memory, whoops
//$strFile = file_get_contents($strDownload);
//set the headers to force a download
header("Content-type: application/force-download");
header("Content-Disposition: attachment; filename=\"".str_replace(" ", "_", $arrCheck['file'])."\"");
//read file to output stream
readfile($strDownload);
http://php.net/manual/en/function.readfile.php