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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Thanku very much .. its working fine in my code
[…] This script has done well for me. __________________ This is not a signature. […]
Thanks for the code! Worked a charm.
I need this to get it to work with Flash-based slideshows like http://www.flashnifties.com/xml_slideshow.php or http://www.maani.us/xml_slideshow. Without download resume support, Flash cannot download the images and generates an error in the slideshow, which means you could only use static images, not ones coming from a script.
Thanks again!
This script is working very well, there is one question I have and it’s late, or early depending on how you look at it, but I can’t get this script to do anything once its completed. I would prefer to have it return true since I am calling it from with in a custom class, but even if i could get it to do a header redirect that would be good.
Thanks so much for the fine work though and any help you can give!
Have you tried simply replacing the last die() with “return true”? I haven’t tested it but I think it should work. This wouldn’t tell you if the file download has completed successfuly (in fact, that would be impossible to know server-side with multithreaded download managers), but you would at least know the downloader has disconnected (but may connect again later if that wasn’t the last chunk to download).
excuse me, i just wanna ask something
what does this part means?
header(“Expires: Mon, 26 Jul 1997 05:00:00 GMT”);
thanks before 🙂
This is supposed to prevent the browser (if a browser is used to download the file) from caching the download. Specifically, it states that the file can only be cached until an arbitrary day in July 1997, which means it will not be cached at all.
[…] use This script. Put it on your server, and make your links point to the script, using the link syntax that they […]
It works in firefox fine. but in IE the save dialog box is not coming.
what could be the reason?
“Blame Microsoft!”
As I might have suggested before, compare headers sent by downloads that show the download box and and those that don’t. See how they differ.
this works well. Thanks
Nice script. Thanks for publishing. 2 questions:
Can I call this after output has started?
Is it possible after calling this function to send another page to the browser?
@pixelterra – It won’t work after output has started unless you are buffering the output. This is because the script needs to send some headers which can only be done before any other (non-header) output is sent.
I don’t think you can send another page after this script, but I suspect you could achieve the result you’re thinking of by sending the “other” page first and adding a meta refresh tag (or something similar, i.e. JS redirect) that will trigger the download.
how to install it?
where do i have to put this?
please answer me… tnx
@Zid – Basically, just put it in a .php file and change the filenames to your own. The script already includes a simple example of use (it’s at the end of the script).
@White Shadow – thanks… (^^,)
@White Shadow – i still have problem … the dowload dialog window didn’t show …
some error :
Warning: Cannot modify header information – headers already sent by (output started at F:\localhost\CURRENT\cngadv\mrp\incl\kondisi.php:65) in F:\localhost\CURRENT\cngadv\mrp\incl\function.php on line 361
Warning: Cannot modify header information – headers already sent by (output started at F:\localhost\CURRENT\cngadv\mrp\incl\kondisi.php:65) in F:\localhost\CURRENT\cngadv\mrp\incl\function.php on line 362
Warning: Cannot modify header information – headers already sent by (output started at F:\localhost\CURRENT\cngadv\mrp\incl\kondisi.php:65) in F:\localhost\CURRENT\cngadv\mrp\incl\function.php on line 363
Warning: Cannot modify header information – headers already sent by (output started at F:\localhost\CURRENT\cngadv\mrp\incl\kondisi.php:65) in F:\localhost\CURRENT\cngadv\mrp\incl\function.php on line 364
Warning: Cannot modify header information – headers already sent by (output started at F:\localhost\CURRENT\cngadv\mrp\incl\kondisi.php:65) in F:\localhost\CURRENT\cngadv\mrp\incl\function.php on line 368
Warning: Cannot modify header information – headers already sent by (output started at F:\localhost\CURRENT\cngadv\mrp\incl\kondisi.php:65) in F:\localhost\CURRENT\cngadv\mrp\incl\function.php on line 369
Warning: Cannot modify header information – headers already sent by (output started at F:\localhost\CURRENT\cngadv\mrp\incl\kondisi.php:65) in F:\localhost\CURRENT\cngadv\mrp\incl\function.php on line 370
Warning: Cannot modify header information – headers already sent by (output started at F:\localhost\CURRENT\cngadv\mrp\incl\kondisi.php:65) in F:\localhost\CURRENT\cngadv\mrp\incl\function.php on line 391
please help me,…. thx
@aseng – Well, I don’t know anything your scripts, so all this tells me is that something already sent some output before calling the output_file() function. Figuring out what did that might solve the problem.
Interesting that you’re using 1MB buffers. Many of the variations of this on the web use 8k buffers. That ends up making a ridiculous amount of IO calls for large files. I was using 32k, but I tried the 1MB buffer as you use here and it seems to reduce CPU usage even further.
@Eric – It’s really a bona-fide optimization problem. Larger buffers save CPU cycles but use up more memory. There are some situations when a script with a smaller buffer would hold up better under heavy load.