PHP: Force download is downloading an empty file

Question

The code below displays this:

/home/my_site/www/wp-content/uploads/2017/03/2017-03-17-my_file.mp3

As far as I can tell, this path is correct. Yet when I comment away the echo and download the file, it's an empty file. Why?

Code:

if (isset($_GET['file'])) { 
    clearstatcache();
    $file_path = str_replace('http://www.example.com/', '', $_GET['file']);
    $file_path = $_SERVER['DOCUMENT_ROOT'] . '/' . $file_path . '.mp3';
    echo $file_path;

    if(file_exists($file_path)) {
        $file_name = basename($file_path);
        $file_size = filesize($file_path);
        header("Cache-Control: private");
        header("Content-Type: application/stream");
        header("Content-Length: ".$file_size);
        header("Content-Disposition: attachment; filename=".$file_name);
        exit();
    }
    else {
        die('The provided file path is not valid.');
    }
}

EDIT: this is what I have after KIKO Software's suggestion. Still downloads empty file.

<?php
if (isset($_GET['file'])) { 
  $file_path = $_SERVER['DOCUMENT_ROOT'] . '/' . $_GET['file'] . '.mp3';
  //echo $file_path;
  //$file_path = $_SERVER['SCRIPT_FILENAME'];  
  if (file_exists($file_path)) {
    $file_name = basename($file_path);
    $file_size = filesize($file_path);
  header('Content-type: application/octet-stream');
  header('Content-Transfer-Encoding: binary');
  header('Content-Length: '.$file_size);
  header('Content-Disposition: attachment; filename='.$file_name);
  //readfile($file_path);
  exit();
  }
  else {
      die('The provided file path is not valid.');
  }
}
?>

score 4 · Accepted Answer · edited May 23 '17 at 12:25

4

Simple example to download a file:

$content = 'This is the content.';
$size    = strlen($content);
$name    = 'test.txt';
header('Content-type: application/octet-stream');
header('Content-Transfer-Encoding: binary');
header('Content-Length: '.$size);
header('Content-Disposition: attachment; filename='.$name);
echo $content;

Make sure this works first. If it doesn't there could be a problem with the headers. Switch on error reporting and see: How to fix "Headers already sent" error in PHP

Then build up on that. Start by downloading the script itself:

$file_path = $_SERVER['SCRIPT_FILENAME'];  
if (file_exists($file_path)) {
  $file_name = basename($file_path);
  $file_size = filesize($file_path);
  header('Content-type: application/octet-stream');
  header('Content-Transfer-Encoding: binary');
  header('Content-Length: '.$file_size);
  header('Content-Disposition: attachment; filename='.$file_name);
  readfile($file_path);
  exit();
}
else {
  die('The provided file path is not valid.');
}

And only after that try to download something else.

By approaching the problem step by step it is easier to see where it goes wrong.

edited May 23 '17 at 12:25

Community

1
1

answered Apr 02 '17 at 10:46

KIKO Software

15,283
3
18
33

If I do that Firefox crashes and there's no file download at all... In Chrome I see the (gibberish) content of the file, no file download either. – drake035 Apr 03 '17 at 08:18
I have to admit, I didn't test your code. The `readfile()` is correct, so that's not causing the problem you have. I changed your headers slightly, perhaps that will help? They were not the standard ones. Also read the manual on `readfile()` when you are using an url. **A URL can be used as a filename with this function if the fopen wrappers have been enabled.** – KIKO Software Apr 03 '17 at 12:22
Also see: https://stackoverflow.com/help/mcve if you want people to give you working code. – KIKO Software Apr 03 '17 at 12:29
Thanks! However your code triggers download of an empty file too. – drake035 Apr 03 '17 at 17:07
Try simple content. So instead of reading and outputting a file, simply `echo '1234567890';` and see if you can download that. After that, make sure your PHP has permission to read the file. – KIKO Software Apr 03 '17 at 19:23
It sounds all good but I'm sorry I have no idea how to do that... For the test you're prescribing, what should I set in lines like header("Content-Length: ".$file_size); ? – drake035 Apr 04 '17 at 08:08
No. I changed by answer to explain it. – KIKO Software Apr 04 '17 at 08:22
Both the first and second snippet work! From there I'll try to go nearer to my case later on today and report back. – drake035 Apr 04 '17 at 09:47
Just tried your second script (which works) and simply replaced $file_path = $_SERVER['SCRIPT_FILENAME']; with my file's path. Downloads empty file again... If I don't comment away readfile($file_path); Firefox crashes. Argh. – drake035 Apr 04 '17 at 20:16
So the problem is in your file's path? It is probably something else, as well. Firefox crashing is a strong indication of a `header()` problem. Basically the headers are not sent to the browser because something else has already been sent. This means that Firefox is trying to render the MP3 as a web page, can't do that, and crashes. See my answer for a link. When you say; "and simply replaced .. with my file's path", are you sure that is really the absolute only thing you do?? Remember: Step by step. – KIKO Software Apr 04 '17 at 21:17
Not sure what I was doing, but it works now. Thanks :) Any idea why the bounty is gone? I'd like to award the +50 to you but there's no mention of bounty any more – drake035 Apr 05 '17 at 14:42
I never saw a bounty, nor have I got any idea how that works. Never mind, I don't do it for the points anyway. – KIKO Software Apr 05 '17 at 15:29
Ah I thought I had started one on that thread. Thanks anyway! – drake035 Apr 05 '17 at 21:23

PHP: Force download is downloading an empty file

1 Answers1