php, file download

Question

I am using the simple file downloading script:

if (file_exists($file)) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename='.basename($file));
    header('Content-Transfer-Encoding: binary');
    header('Expires: 0');
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    header('Pragma: public');
    header('Content-Length: ' . filesize($file));
    ob_clean();
    flush();
    readfile($file);
    exit;
}

It is working on my localserver upto 200mb.

When i try this code in my website it downloads 173KB instead of 200MB file.

I checked everything, wrote some custom code (using ob functions and fread instead of readfile) but can't download big files.

Thank you for your answers.

I am using Apache 2.2, PHP 5.3
All PHP settings to deal with big files are ok. (execution times, memory limits, ...

my hosting, dreamhost sometimes kills scripts consuming much cpu or resource. That could be your case. — nerkn, Apr 08 '11 at 13:18

score 21 · Accepted Answer · edited May 23 '17 at 12:17

One issue I have with the following code is you have no control over the output stream, your letting PHP handle it without knowing exactly what is going on within the background:

What you should do is set up an output system that you can control and replicated accros servers.

For example:

if (file_exists($file))
{
    if (FALSE!== ($handler = fopen($file, 'r')))
    {
        header('Content-Description: File Transfer');
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename='.basename($file));
        header('Content-Transfer-Encoding: chunked'); //changed to chunked
        header('Expires: 0');
        header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
        header('Pragma: public');
        //header('Content-Length: ' . filesize($file)); //Remove

        //Send the content in chunks
        while(false !== ($chunk = fread($handler,4096)))
        {
            echo $chunk;
        }
    }
    exit;
}
echo "<h1>Content error</h1><p>The file does not exist!</p>";

This is only basic but give it a go!

Also read my reply here: file_get_contents => PHP Fatal error: Allowed memory exhausted

Thanks. Chunked sending is working on all servers without problem. Also i am sending the filesize, actually sending complete filesize and sending the file chunk by chunk may trivial but it works good for now. Otherwise for big downloads user won't see the complete filesize and this may not good for usability. — jsonx, Apr 10 '11 at 13:52
It's totally depends on how the data would be transferred, for instance streaming and downloading are require 2 separate methods of content delivery. glad to help — RobertPitt, Apr 10 '11 at 21:23
Shouldn't `base name($file)` be encoded? What if it contains characters that screw with http? — 735Tesla, Jan 02 '14 at 00:07

score 3 · Answer 2 · answered Nov 30 '12 at 21:05

One solution to certain scenarios is that you can use PHP-script to intelligently decide what file from where to download, but instead of sending the file directly from PHP, you could return a redirection to the client which then contains the direct link which is processed by the web server alone.

This could be done at least in two ways: either PHP-script copies the file into a "download zone" which for example might be cleaned from "old" files regularly by some other background/service script or you expose the real permanent location to the clients.

There are of course drawbacks as is the case with each solution. In this one is that depending on the clients (curl, wget, GUI browser) requesting the file they may not support redirection you make and in the other one, the files are very exposed to the outer world and can be at all times read without the (access) control of the PHP script.

score 3 · Answer 3 · edited Jun 20 '20 at 09:12

3

It seems readfile can have issues with long files. As @Khez asked, it could be that the script is running for too long. A quick Googling resulted in a couple examples of chunking the file.

http://teddy.fr/blog/how-serve-big-files-through-php http://www.php.net/manual/en/function.readfile.php#99406

edited Jun 20 '20 at 09:12

Community

1
1

answered Apr 08 '11 at 13:23

Paul DelRe

4,003
1
24
26

all settings are fine to work with big files, execution times, memory limits, ... – jsonx Apr 08 '11 at 13:46
in the first link's read_chunked() function solved the problem. – jsonx Apr 08 '11 at 13:53

score 0 · Answer 4 · answered Apr 08 '11 at 13:11

0

Have you made sure your script can run long enough and has enough memory?

Do you really need output buffering ?

answered Apr 08 '11 at 13:11

Khez

10,172
2
31
51

score 0 · Answer 5 · answered Apr 08 '11 at 13:40

The real solution is to avoid using a PHP script for just sending a file to the client, it's overkill and your webserver is better suited for the task.

Presumably you have a reason for sending the files through PHP, perhaps users must authenticate first? If that is the case then you should use X-Accel-Redirect (if you're using nginx) or X-Sendfile (previously X-LIGHTTPD-send-file) on lighttpd.

If you're using Apache I've found a few references to mod_xsendfile but I've never used it personally, and I doubt it's installed for you if you have managed hosting.

If these solutions are untenable I apologise, but I really need more information on the actual problem: Why are you sending these files through PHP in the first place?

Thank you Zofrex, yes there must be done some authentication and some other operations before sending files. mod_xsendfile looks good, i will try it. It maybe the clearer solution. — jsonx, Apr 08 '11 at 14:05

php, file download

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