How To Force File Download With PHP
Say you want a PHP script that will make the browser to download a file instead of opening it. This is useful for common filetypes that would normally be displayed in a browser, like .html, images, PDFs and .doc files.
You can find a lot of scripts that do this on the web but one thing most of them don’t handle is download resuming and multi-thread downloading. If you don’t need that feature, feel free to use a simpler script. Personally I’ve found that a function that handles download resuming works more reliably across various browsers (what actually happened : a simpler script didn’t work with Opera + my weird Internet connection, so I found another script and decided to make broad generalizations about download resuming :p).
Note – most of the code below isn’t mine. I found it somewhere on the web and adjusted it for my needs; unfortunately I’ve lost the URL of the original page. If you know where it came from, let me know and I’ll add a link to this post.
function output_file($file, $name, $mime_type=”)
{
/*
This function takes a path to a file to output ($file),
the filename that the browser will see ($name) and
the MIME type of the file ($mime_type, optional).
If you want to do something on download abort/finish,
register_shutdown_function(‘function_name’);
*/
if(!is_readable($file)) die(‘File not found or inaccessible!’);
$size = filesize($file);
$name = rawurldecode($name);
/* Figure out the MIME type (if not specified) */
$known_mime_types=array(
“pdf” => “application/pdf”,
“txt” => “text/plain”,
“html” => “text/html”,
“htm” => “text/html”,
“exe” => “application/octet-stream”,
“zip” => “application/zip”,
“doc” => “application/msword”,
“xls” => “application/vnd.ms-excel”,
“ppt” => “application/vnd.ms-powerpoint”,
“gif” => “image/gif”,
“png” => “image/png”,
“jpeg”=> “image/jpg”,
“jpg” => “image/jpg”,
“php” => “text/plain”
);
if($mime_type==”){
$file_extension = strtolower(substr(strrchr($file,”.”),1));
if(array_key_exists($file_extension, $known_mime_types)){
$mime_type=$known_mime_types[$file_extension];
} else {
$mime_type=”application/force-download”;
};
};
@ob_end_clean(); //turn off output buffering to decrease cpu usage
// required for IE, otherwise Content-Disposition may be ignored
if(ini_get(‘zlib.output_compression’))
ini_set(‘zlib.output_compression’, ‘Off’);
header(‘Content-Type: ‘ . $mime_type);
header(‘Content-Disposition: attachment; filename=”‘.$name.'”‘);
header(“Content-Transfer-Encoding: binary”);
header(‘Accept-Ranges: bytes’);
/* The three lines below basically make the
download non-cacheable */
header(“Cache-control: private”);
header(‘Pragma: private’);
header(“Expires: Mon, 26 Jul 1997 05:00:00 GMT”);
// multipart-download and download resuming support
if(isset($_SERVER[‘HTTP_RANGE’]))
{
list($a, $range) = explode(“=”,$_SERVER[‘HTTP_RANGE’],2);
list($range) = explode(“,”,$range,2);
list($range, $range_end) = explode(“-“, $range);
$range=intval($range);
if(!$range_end) {
$range_end=$size-1;
} else {
$range_end=intval($range_end);
}
$new_length = $range_end-$range+1;
header(“HTTP/1.1 206 Partial Content”);
header(“Content-Length: $new_length”);
header(“Content-Range: bytes $range-$range_end/$size”);
} else {
$new_length=$size;
header(“Content-Length: “.$size);
}
/* output the file itself */
$chunksize = 1*(1024*1024); //you may want to change this
$bytes_send = 0;
if ($file = fopen($file, ‘r’))
{
if(isset($_SERVER[‘HTTP_RANGE’]))
fseek($file, $range);
while(!feof($file) &&
(!connection_aborted()) &&
($bytes_send<$new_length)
)
{
$buffer = fread($file, $chunksize);
print($buffer); //echo($buffer); // is also possible
flush();
$bytes_send += strlen($buffer);
}
fclose($file);
} else die('Error - can not open file.');
die();
}
/*********************************************
Example of use
**********************************************/
/*
Make sure script execution doesn't time out.
Set maximum execution time in seconds (0 means no limit).
*/
set_time_limit(0);
$file_path='that_one_file.txt';
output_file($file_path, 'some file.txt', 'text/plain');
[/sourcecode]
Related info
Determining MIME type of a file automatically
Common MIME types
HTTP, caching and other stuff
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Thanks for the function! One issue:
While the browser (Firefox) is downloading a file outputted by this function, it does not appear to know the total size of the file. So there is no download progress and the download status reads something like “downloaded 3.5MB of unknown”. Is that something we can fix?
The total size does appear for me when using Firefox, so I don’t know about that. However, your question prompted me to review the code and I found a (non-critical) bug, which I have now fixed (I think). You can try the modified function and see if that helps any.
Strange. I’m still getting “unknown file size” with Firefox or IE7. Thanks for your help!
(Sorry for the late response. Forgot to check back here.)
Strange indeed. Oh well 🙂
Thank you for your script! I tried a few others, and no matter what I did, powerpoint files were coming through with a filesize of zero bytes. Using this script however, I am able to get the file to come through properly.
I do have one problem though. I am programming my site for Japanese (I work in a Japanese company), and when I call the function with $name using Japanese text, it comes through garbled. I have tried using header(‘Accept-Charset: Shift_JIS’) and header(‘Content-Type: ‘ . $mime_type ‘; charset=Shift_JIS’); and a combination of both, but they don’t seem to work. I have also tried using the other two types of Japanese encoding, and they dont seem to work either. Any ideas?
I don’t have a complete solution, but here are some ideas :
* Use a HTTP header viewer and look what headers are sent by other websites that display the filename correctly. For example, if you have FireFox, you could use the LiveHTTPHeaders addon for this.
* When you set charset=whatever, are you sure you’re using the same charset in your PHP file? Maybe it’s actually Unicode?
* See this page – HTTP headers and non-ASCI characters
Thanks so much for this script! I was looking for a way to force the download of a vcard off my website and this did the trick!
hi
the code for download works fine for me…
thank you very much…
For some reason it is not working for me. I have these attributes assigned in my downloadfile.php:
filename: test.12.docfiletype: application/msword
filepath: /files/15.attach
I call it using the function that is in this article using the following:
output_file($filepath, $filename, $filetype);However, I get this error:
File not found or inaccessible!OOPS! If anyone has a solution for the above problem, please email me at mrd3sai@gmail.com (Thanks)
A path that starts with a forward slash will be interpreted as an absolute path by most operating systems, which is probably not what you want to do here. If you need the script to download the file “15.attach” from a folder called “files” that is in the same directory as the script, you should use “file/15.attach”, not “/file/15.attach”.
Found out the bug was in my functions.php file. I had a space at the end and because headers don’t do well if something is already outputted, it was erroring out.
Just wanted to say thanks – helped me get something done at work. I’ve left the URL of this page in the PHP comments in case anyone other than me works on that partic script 🙂
Glad to help 🙂
Very nice.
I am also getting the filesize problem. filesize($file); returns the correct filesize, so I can only assume the browser (firefox/ie7) is not figuring out the header.
This happens with other download scripts I have seen. For example, the simplest way of doing it:
header(‘Content-Length: ‘.filesize($file));
has the same problem.
Just tested again with the first download manager in google (http://www.freedownloadmanager.org) and size is given correctly, resume works nicely etc. Good job.
Doesn’t help explain browsers though(?)
I can’t add much to what you said.
However, you might be able to locate the cause by looking at the complete HTTP headers for a download that displays the file size, and the one that doesn’t. See what the difference is.
I’m too lazy to do it myself 😛
Another thing Mr. Shadow. What would you say is the most robust way of implementing this?
At the moment I have a page which fetches the information about the download. Currently, the file path is put in a session variable, and a link is given on this page to download.php. download.php contains you script. It looks at the session variable, and calls output_file accordingly.
But it is not perfect. For example, if I cancel the download in firefox half way, then click the download.php link a second time to restart it, nothing happens. (Similarly, clicking retry in firefox attempts to download download.php rather than the correct file).
Cheers
I think the obvious way would be to pass the information to download.php in a URL parameter. Though you probably don’t want the user to know the file path (right?). For this, there are many possible solutions :
* Store the file path in a database and pass an unique ID to download.php, e.g. “download.php?id=123”. Make the download script get the appropriate path from the DB. This is probably what I would do.
* Do the same thing but instead of a DB save the ID/filepath pairs in a file.
* Encrypt the file path and pass it to the script. You could use the mcrypt module, or something like this encryption class
Use what best fits your situation.
‘Robustivness’ problem identified. In my case, session_start() at the start of download.php. Calling a session messes up the flow I suppose. I will be implementing the db approach.
Still no clues about filesize.
Thanks again