PHP Unconference Europe 2015

readfile

(PHP 4, PHP 5)

readfileOutputs a file

Description

int readfile ( string $filename [, bool $use_include_path = false [, resource $context ]] )

Reads a file and writes it to the output buffer.

Parameters

filename

The filename being read.

use_include_path

You can use the optional second parameter and set it to TRUE, if you want to search for the file in the include_path, too.

context

A context stream resource.

Return Values

Returns the number of bytes read from the file. If an error occurs, FALSE is returned and unless the function was called as @readfile(), an error message is printed.

Examples

Example #1 Forcing a download using readfile()

<?php
$file 
'monkey.gif';

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

The above example will output something similar to:

Open / Save dialogue

Notes

Note:

readfile() will not present any memory issues, even when sending large files, on its own. If you encounter an out of memory error ensure that output buffering is off with ob_get_level().

Tip

A URL can be used as a filename with this function if the fopen wrappers have been enabled. See fopen() for more details on how to specify the filename. See the Supported Protocols and Wrappers for links to information about what abilities the various wrappers have, notes on their usage, and information on any predefined variables they may provide.

Note: Context support was added with PHP 5.0.0. For a description of contexts, refer to Streams.

See Also

add a note add a note

User Contributed Notes 31 notes

up
7
marro at email dot cz
6 years ago
My script working correctly on IE6 and Firefox 2 with any typ e of files (I hope :))

function DownloadFile($file) { // $file = include path
        if(file_exists($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;
        }

    }

Run on Apache 2 (WIN32) PHP5
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4
yura_imbp at mail dot ru
6 years ago
if you need to limit download rate, use this code

<?php
$local_file
= 'file.zip';
$download_file = 'name.zip';

// set the download rate limit (=> 20,5 kb/s)
$download_rate = 20.5;
if(
file_exists($local_file) && is_file($local_file))
{
   
header('Cache-control: private');
   
header('Content-Type: application/octet-stream');
   
header('Content-Length: '.filesize($local_file));
   
header('Content-Disposition: filename='.$download_file);

   
flush();
   
$file = fopen($local_file, "r");
    while(!
feof($file))
    {
       
// send the current file part to the browser
       
print fread($file, round($download_rate * 1024));
       
// flush the content to the browser
       
flush();
       
// sleep one second
       
sleep(1);
    }
   
fclose($file);}
else {
    die(
'Error: The file '.$local_file.' does not exist!');
}

?>
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4
TimB
6 years ago
To anyone that's had problems with Readfile() reading large files into memory the problem is not Readfile() itself, it's because you have output buffering on. Just turn off output buffering immediately before the call to Readfile(). Use something like ob_end_flush().
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2
Anonymous
9 years ago
here is a nice force download scirpt

            $filename = 'dummy.zip';
            $filename = realpath($filename);

            $file_extension = strtolower(substr(strrchr($filename,"."),1));

            switch ($file_extension) {
                case "pdf": $ctype="application/pdf"; break;
                case "exe": $ctype="application/octet-stream"; break;
                case "zip": $ctype="application/zip"; break;
                case "doc": $ctype="application/msword"; break;
                case "xls": $ctype="application/vnd.ms-excel"; break;
                case "ppt": $ctype="application/vnd.ms-powerpoint"; break;
                case "gif": $ctype="image/gif"; break;
                case "png": $ctype="image/png"; break;
                case "jpe": case "jpeg":
                case "jpg": $ctype="image/jpg"; break;
                default: $ctype="application/force-download";
            }

            if (!file_exists($filename)) {
                die("NO FILE HERE");
            }

            header("Pragma: public");
            header("Expires: 0");
            header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
            header("Cache-Control: private",false);
            header("Content-Type: $ctype");
            header("Content-Disposition: attachment; filename=\"".basename($filename)."\";");
            header("Content-Transfer-Encoding: binary");
            header("Content-Length: ".@filesize($filename));
            set_time_limit(0);
            @readfile("$filename") or die("File not found.");
up
1
riksoft at gmail dot com
8 months ago
Just a note for those who face problems on names containing spaces (e.g. "test test.pdf").

In the examples (99% of the time) you can find
header('Content-Disposition: attachment; filename='.basename($file));

but the correct way to set the filename is quoting it (double quote):
header('Content-Disposition: attachment; filename="'.basename($file).'"' );

Some browsers may work without quotation, but for sure not Firefox and as Mozilla explains, the quotation of the filename in the content-disposition is according to the RFC
http://kb.mozillazine.org/Filenames_with_spaces_are_truncated_upon_download
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2
chrisputnam at gmail dot com
9 years ago
In response to flowbee@gmail.com --

When using the readfile_chunked function noted here with files larger than 10MB or so I am still having memory errors. It's because the writers have left out the all important flush() after each read. So this is the proper chunked readfile (which isn't really readfile at all, and should probably be crossposted to passthru(), fopen(), and popen() just so browsers can find this information):

<?php
function readfile_chunked($filename,$retbytes=true) {
  
$chunksize = 1*(1024*1024); // how many bytes per chunk
  
$buffer = '';
  
$cnt =0;
  
// $handle = fopen($filename, 'rb');
  
$handle = fopen($filename, 'rb');
   if (
$handle === false) {
       return
false;
   }
   while (!
feof($handle)) {
      
$buffer = fread($handle, $chunksize);
       echo
$buffer;
      
ob_flush();
      
flush();
       if (
$retbytes) {
          
$cnt += strlen($buffer);
       }
   }
      
$status = fclose($handle);
   if (
$retbytes && $status) {
       return
$cnt; // return num. bytes delivered like readfile() does.
  
}
   return
$status;

}
?>

All I've added is a flush(); after the echo line. Be sure to include this!
up
1
Hayley Watson
7 years ago
To avoid the risk of choosing themselves which files to download by messing with the request and doing things like inserting "../" into the "filename", simply remember that URLs are not file paths, and there's no reason why the mapping between them has to be so literal as "download.php?file=thingy.mpg" resulting in the download of the file "thingy.mpg".

It's your script and you have full control over how it maps file requests to file names, and which requests retrieve which files.

But even then, as ever, never trust ANYTHING in the request. Basic first-day-at-school security principle, that.
up
1
Brian
8 months ago
If you are looking for an algorithm that will allow you to download (force download) a big file, may this one will help you.

$filename = "file.csv";
$filepath = "/path/to/file/" . $filename;

// Close sessions to prevent user from waiting until
// download will finish (uncomment if needed)
//session_write_close();

set_time_limit(0);
ignore_user_abort(false);
ini_set('output_buffering', 0);
ini_set('zlib.output_compression', 0);

$chunk = 10 * 1024 * 1024; // bytes per chunk (10 MB)

$fh = fopen($filepath, "rb");

if ($fh === false) {
    echo "Unable open file";
}

header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="' . $filename . '"');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($filepath));

// Repeat reading until EOF
while (!feof($fh)) {
    echo fread($handle, $chunk);
   
    ob_flush();  // flush output
    flush();
}

exit;
up
1
mAu
8 years ago
Instead of using
<?php
header
('Content-Type: application/force-download');
?>
use
<?php
header
('Content-Type: application/octet-stream');
?>
Some browsers have troubles with force-download.
up
0
kevin dot goodman at itmsoil dot com
1 year ago
I wasted days trying to figure this out before I found the problem was easily solved.

I'm sure many of you out there have had similar problem when trying to use readfile to output images with a php file as the "src" of a "img" tag.
It works fine "as is" in Firefox but not in IE, Safari or g.Chrome.

I found hundreds of results on google all saying things like "there must be white space at the end of you code", "you need this header or that header".
I couldn't believe what the solution was but here it is anyway!

Remove the "Width" and "Height" attributes from your "img" tag
up
0
daren -remove-me- schwenke
3 years ago
If you are lucky enough to not be on shared hosting and have apache, look at installing mod_xsendfile.
This was the only way I found to both protect and transfer very large files with PHP (gigabytes). 
It's also proved to be much faster for basically any file.
Available directives have changed since the other note on this and XSendFileAllowAbove was replaced with XSendFilePath to allow more control over access to files outside of webroot.

Download the source.

Install with: apxs -cia mod_xsendfile.c

Add the appropriate configuration directives to your .htaccess or httpd.conf files:
# Turn it on
XSendFile on
# Whitelist a target directory.
XSendFilePath /tmp/blah

Then to use it in your script:
<?php
$file
= '/tmp/blah/foo.iso';
$download_name = basename($file);
if (
file_exists($file)) {
   
header('Content-Type: application/octet-stream');
   
header('Content-Disposition: attachment; filename='.$download_name);
   
header('X-Sendfile: '.$file);
    exit;
}
?>
up
0
levhita at gmail dot com
6 years ago
A note on the smartReadFile function from gaosipov:

Change the indexes on the preg_match matches to:
     
      $begin = intval($matches[1]);
      if( !empty($matches[2]) ) {
        $end = intval($matches[2]);
      }

Otherwise the $begin would be set to the entire section matched and the $end to what should be the begin.

See preg_match for more details on this.
up
0
gaosipov at gmail dot com
6 years ago
Send file with HTTPRange support (partial download):

<?php
function smartReadFile($location, $filename, $mimeType='application/octet-stream')
{ if(!
file_exists($location))
  {
header ("HTTP/1.0 404 Not Found");
    return;
  }
 
 
$size=filesize($location);
 
$time=date('r',filemtime($location));
 
 
$fm=@fopen($location,'rb');
  if(!
$fm)
  {
header ("HTTP/1.0 505 Internal server error");
    return;
  }
 
 
$begin=0;
 
$end=$size;
 
  if(isset(
$_SERVER['HTTP_RANGE']))
  { if(
preg_match('/bytes=\h*(\d+)-(\d*)[\D.*]?/i', $_SERVER['HTTP_RANGE'], $matches))
    {
$begin=intval($matches[0]);
      if(!empty(
$matches[1]))
       
$end=intval($matches[1]);
    }
  }
 
  if(
$begin>0||$end<$size)
   
header('HTTP/1.0 206 Partial Content');
  else
   
header('HTTP/1.0 200 OK'); 
 
 
header("Content-Type: $mimeType");
 
header('Cache-Control: public, must-revalidate, max-age=0');
 
header('Pragma: no-cache'); 
 
header('Accept-Ranges: bytes');
 
header('Content-Length:'.($end-$begin));
 
header("Content-Range: bytes $begin-$end/$size");
 
header("Content-Disposition: inline; filename=$filename");
 
header("Content-Transfer-Encoding: binary\n");
 
header("Last-Modified: $time");
 
header('Connection: close'); 
 
 
$cur=$begin;
 
fseek($fm,$begin,0);

  while(!
feof($fm)&&$cur<$end&&(connection_status()==0))
  { print
fread($fm,min(1024*16,$end-$cur));
   
$cur+=1024*16;
  }
}
?>

Usage:

<?php
smartReadFile
("/tmp/filename","myfile.mp3","audio/mpeg")
?>

It can be slow for big files to read by fread, but this is a single way to read file in strict bounds. You can modify this and add fpassthru instead of fread and while, but it sends all data from begin --- it would be not fruitful if request is bytes from 100 to 200 from 100mb file.
up
-1
Anonymous
13 days ago
<form action = "open.php" method = "post" >
<input ="text" name ="brian" >
<input type = "submit" name = "download" value = "download">
</form>
<?php

if(isset($_POST['download']))
{
$img ='img';
$pic = '\marcus2';
$fad = 'pdf';

$file = $img.''. $pic .'.'. $fad;

echo
$file;

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

}

?>
up
-1
peavey at pixelpickers dot com
9 years ago
A mime-type-independent forced download can also be conducted by using:

<?
(...)
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); // some day in the past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
header("Content-type: application/x-download");
header("Content-Disposition: attachment; filename={$new_name}");
header("Content-Transfer-Encoding: binary");
?>

Cheers,

Peavey
up
-1
johniskew
6 years ago
@marks suggestion-

That is one way to do it, however this is avoidable.  For example in Zend Framework you could do

<?php

// Action controller
public function someAction() {

   
$response = $this->_response;

   
// Disable view and layout rendering
   
$this->_helper->viewRenderer->setNoRender();
   
$this->_helper->layout()->disableLayout();

   
// Process the file
   
$file = 'whatever.zip';
   
$bits = @file_get_contents($file);
    if(
strlen($bits) == 0) {
       
$response->setBody('Sorry, we could not find requested download file.');
    }
    else {
       
$response->setHeader('Content-type', 'application/octet-stream', true);
       
$response->setBody($bits);
    }
}

?>
up
-1
chad 0x40 herballure 0x2e com
7 years ago
In reply to herbert dot fischer at NOSPAM dot gmail dot com:

The streams API in PHP5 tries to make things as efficient as possible; in php-5.1.6 on Linux, fpassthru is faster than 'echo fread($fp, 8192)' in a loop, and readfile is even faster for files on disk. I didn't benchmark further, but I'd be willing to bet non-mmap'able streams still win because they can loop in C instead of PHP.
up
-1
Elliott Brueggeman
7 years ago
I have noticed some unusual behavior with Internet Explorer 6 that’s worth taking note of. I have a link on my site to a script that outputs an XML file to the browser with the below code:

header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="'.$filename.'"');
@readfile($file);

When the popular IE setting “Reuse Window for Launching Shortcuts” is unchecked (access this setting in the Tools Menu > Internet Options > Advanced Tab) this script will output the file to the browser and open it in a different window if the user clicks the open button on the IE prompt. However, if this setting is checked, and browser windows are being re-used, then it will open up on top of the page where the link was clicked to access the script.

If I instead set the html link target option to be “_blank”, the script will open up in a new window as expected if the “Reuse Window for Launching Shortcuts” is checked. But, if the setting is unchecked, the output XML file will open up in a new window and there will be another blank window also open that has the address of the script, in addition to our original window.

This is far from ideal, and there is no way of knowing whether users have this option checked or not. We are stuck with the distinct possibility of half of our visitors seeing either an annoying third blank window being opened or the script writing over their original window, depending on their “Reuse Window for Launching Shortcuts” setting.
up
-1
planetmaster at planetgac dot com
9 years ago
Using pieces of the forced download script, adding in MySQL database functions, and hiding the file location for security was what we needed for downloading wmv files from our members creations without prompting Media player as well as secure the file itself and use only database queries. Something to the effect below, very customizable for private access, remote files, and keeping order of your online media.

<?
   
# Protect Script against SQL-Injections
   
$fileid=intval($_GET[id]);
   
# setup SQL statement
   
$sql = " SELECT id, fileurl, filename, filesize FROM ibf_movies WHERE id=' $fileid' ";

   
# execute SQL statement
   
$res = mysql_query($sql);

       
# display results
       
while ($row = mysql_fetch_array($res)) {
       
$fileurl = $row['fileurl'];
       
$filename= $row['filename'];
       
$filesize= $row['filesize'];

          
$file_extension = strtolower(substr(strrchr($filename,"."),1));

           switch (
$file_extension) {
               case
"wmv": $ctype="video/x-ms-wmv"; break;
               default:
$ctype="application/force-download";
           }

// required for IE, otherwise Content-disposition is ignored
if(ini_get('zlib.output_compression'))
ini_set('zlib.output_compression', 'Off');

          
header("Pragma: public");
          
header("Expires: 0");
          
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
          
header("Cache-Control: private",false);
          
header("Content-Type: video/x-ms-wmv");
          
header("Content-Type: $ctype");
          
header("Content-Disposition: attachment; filename=\"".basename($filename)."\";");
          
header("Content-Transfer-Encoding: binary");
          
header("Content-Length: ".@filesize($filename));
          
set_time_limit(0);
           @
readfile("$fileurl") or die("File not found.");

}

$donwloaded = "downloads + 1";

    if (
$_GET["hit"]) {
       
mysql_query("UPDATE ibf_movies SET downloads = $donwloaded WHERE id=' $fileid'");

}

?>

While at it I added into download.php a hit (download) counter. Of course you need to setup the DB, table, and columns. Email me for Full setup// Session marker is also a security/logging option
Used in the context of linking:
http://www.yourdomain.com/download.php?id=xx&hit=1

[Edited by sp@php.net: Added Protection against SQL-Injection]
up
-1
Philipp Heckel
9 years ago
To use readfile() it is absolutely necessary to set the mime-type before. If you are using an Apache, it's quite simple to figure out the correct mime type. Apache has a file called "mime.types" which can (in normal case) be read by all users.

Use this (or another) function to get a list of mime-types:

<?php

   
function mimeTypes($file) {
        if (!
is_file($file) || !is_readable($file)) return false;
       
$types = array();
       
$fp = fopen($file,"r");
        while (
false != ($line = fgets($fp,4096))) {
            if (!
preg_match("/^\s*(?!#)\s*(\S+)\s+(?=\S)(.+)/",$line,$match)) continue;
           
$tmp = preg_split("/\s/",trim($match[2]));
            foreach(
$tmp as $type) $types[strtolower($type)] = $match[1];
        }
       
fclose ($fp);
       
        return
$types;
    }

   
# [...]

    # read the mime-types
   
$mimes = mimeTypes('/usr/local/apache/current/conf/mime.types');

   
# use them ($ext is the extension of your file)
   
if (isset($mimes[$ext])) header("Content-Type: ".$mimes[$ext]);
   
header("Content-Length: ".@filesize($fullpath));
   
readfile($fullpath); exit;

?>

If you do not want to read from the mime.types file directly, you can of course make a copy in another folder!
Cheers Philipp Heckel
up
-1
flobee at gmail dot com
9 years ago
regarding php5:
i found out that there is already a disscussion @php-dev  about readfile() and fpassthru() where only exactly 2 MB will be delivered.

so you may use this on php5 to get lager files
<?php
function readfile_chunked($filename,$retbytes=true) {
   
$chunksize = 1*(1024*1024); // how many bytes per chunk
   
$buffer = '';
   
$cnt =0;
   
// $handle = fopen($filename, 'rb');
   
$handle = fopen($filename, 'rb');
    if (
$handle === false) {
        return
false;
    }
    while (!
feof($handle)) {
       
$buffer = fread($handle, $chunksize);
        echo
$buffer;
        if (
$retbytes) {
           
$cnt += strlen($buffer);
        }
    }
       
$status = fclose($handle);
    if (
$retbytes && $status) {
        return
$cnt; // return num. bytes delivered like readfile() does.
   
}
    return
$status;

}
?>
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-1
TheDayOfCondor
9 years ago
I think that readfile suffers from the maximum script execution time. The readfile is always completed even if it exceed the default 30 seconds limit, then the script is aborted.
Be warned that you can get very odd behaviour not only on large files, but also on small files if the user has a slow connection.

The best thing to do is to use

<?
  set_time_limit
(0);
?>

just before the readfile, to disable completely the watchdog if you intend to use the readfile call to tranfer a file to the user.
up
-1
TheDayOfCondor
9 years ago
Beware - the chunky readfile suggested by Rob Funk can easily exceed you maximum script execution time (30 seconds by default).

I suggest you to use the set_time_limit function inside the while loop to reset the php watchdog.
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-1
Thomas Jespersen
10 years ago
Remember if you make a "force download" script like mentioned below that you SANITIZE YOUR INPUT!

I have seen a lot of  download scripts that does not test so you are able to download anything you want on the server.

Test especially for strings like ".." which makes directory traversal possible. If possible only permit characters a-z, A-Z and 0-9 and make it possible to only download from one "download-folder".
up
-2
sakai at d4k dot net
5 years ago
To reduce the burden on the server, you might want to output "Etag" and/or "Last-Modified" on http response header.  But there are some headers, which PHP itself outputs automatically, disturbing this.  So I wrote this function with erasing these.

If you guys know how to judge the return values of function "stat", in order to avoid using "is_file" or "is_readable" (or "is_dir"), please let me know or just write it here.

If you don't have to do anything special on 404, "header('HTTP/1.x xxx xxxxx');" can be inside of the function.

<?php

$filename
= '/foo/bar/myfeed.rss';
$http_stat_code = readfile_if_modified($filename, array('Content-Type: text/xml'));
switch(
$http_stat_code) {
case
404:
   
header('HTTP/1.0 404 Not Found');
    echo
'<html><head></head><body><a href="http://example.com/">http://example.com/<a></body></html>';
    exit;
default:
   
header('X-System-Url: http://example.com/', true, $http_stat_code);
}

function
readfile_if_modified($filename, $http_header_additionals = array()) {

    if(!
is_file($filename)) {
//      header('HTTP/1.0 404 Not Found');
       
return 404;
    }

    if(!
is_readable($filename)) {
//      header('HTTP/1.0 403 Forbidden');
       
return 403;
    }

   
$stat = @stat($filename);
   
$etag = sprintf('%x-%x-%x', $stat['ino'], $stat['size'], $stat['mtime'] * 1000000);

   
header('Expires: ');
   
header('Cache-Control: ');
   
header('Pragma: ');

    if(isset(
$_SERVER['HTTP_IF_NONE_MATCH']) && $_SERVER['HTTP_IF_NONE_MATCH'] == $etag) {
       
header('Etag: "' . $etag . '"');
//      header('HTTP/1.0 304 Not Modified');
       
return 304;
    } elseif(isset(
$_SERVER['HTTP_IF_MODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) >= $stat['mtime']) {
       
header('Last-Modified: ' . date('r', $stat['mtime']));
//      header('HTTP/1.0 304 Not Modified');
       
return 304;
    }

   
header('Last-Modified: ' . date('r', $stat['mtime']));
   
header('Etag: "' . $etag . '"');
   
header('Accept-Ranges: bytes');
   
header('Content-Length:' . $stat['size']);
    foreach(
$http_header_additionals as $header) {
       
header($header);
    }

    if(@
readfile($filename) === false) {
//      header('HTTP/1.0 500 Internal Server Error');
       
return 500;
    } else {
//      header('HTTP/1.0 200 OK');
       
return 200;
    }

}

?>
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-1
Sinured
7 years ago
In response to "grey - greywyvern - com":

If you know the target _can't_ be a remote file (e.g. prefixing it with a directory), you should use include instead.
If the user manages to set the target to some kinda config-file (configuration.php in Joomla!), he will get a blank page - unless readfile() is used. Using include will just behave as a normal request (no output).
For remote files however use readfile().
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-1
Kniht
7 years ago
@Elliott Brueggeman
What's the point of a user's settings if not to determine their environment? If they have it set a specific way, honor their setting.
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-1
antispam [at] rdx page [dot] com
9 years ago
Just a note:  If you're using bw_mod (current version 0.6) to limit bandwidth in Apache 2, it *will not* limit bandwidth during readfile events.
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-2
cOrti
3 years ago
Hello,

Here's a simple trick for browsers (FF, IE) address spaces in filenames for Content-Disposition:

eg: <?php header ("Content-Disposition:attachment; filename=\"$filename\""); ?>

The \ "before and after the file name makes the difference.
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-2
Zambz
4 years ago
If you are using the procedures outlined in this article to force sending a file to a user, you may find that the "Content-Length" header is not being sent on some servers.

The reason this occurs is because some servers are setup by default to enable gzip compression, which sends an additional header for such operations.  This additional header is "Transfer-Encoding: chunked" which essentially overrides the "Content-Length" header and forces a chunked download.  Of course, this is not required if you are using the intelligent versions of readfile in this article.

A missing Content-Length header implies the following:

1) Your browser will not show a progress bar on downloads because it doesn't know their length
2) If you output anything (e.g. white space) after the readfile function (by mistake), the browser will add that to the end of the download, resulting in corrupt data.

The easiest way to disable this behaviour is with the following .htaccess directive.

SetEnv no-gzip dont-vary
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-3
Mike
4 years ago
Beware of using download managers.. I was trying to use readfile in IE8 and kept getting the message "failed to get data for 'type'". Eventually figured out the problem was that I had LeechGet installed and it was intercepting the download, which in turn prevented the download from taking place.
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