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Download Counter with Apache and PHP

Author: Martin Tsachev More by this author

Added: May 27, 2005 Rating:

Level: Beginner Software: PHP Editors

Info: Collect statistics on the popularity of your downloads with Apache's mod_rewrite and PHP.

How some of the others do it

Some sites present you an URI like http://www.example.com/download.php?file=/foo/bar, which is less than perfect. Being a Windows user (well sometimes) I expect that when I add a file to my download manager I'll see the filename in the list - unfortunately the result from adding a file from such a link is the meaningless download.php in your file list.

While the method mentioned above is easy to implement it is not the best way to do it. We want visitors to see the real filename as the URI not as a query string. So what we'll do internally is exactly the same as in the above example but this time the visitor will see the real filename.

How do we do it

Our URIs will be in the form of http://www.example.com/foo/bar which makes more sense, doesn't it?

What do we need

Apache compiled with mod_rewrite (off by default, you need to add --enable-module=rewrite to your configure line)
PHP as the scripting engine
A database, like MySQL, to store the download data

Apache's configuration

Options +FollowSymLinks
RewriteEngine On
RewriteBase /foobar/
RewriteRule download/send.php - [L]
RewriteRule download/(.+..+)$ download/send.php?file=$1 [L]

You can put this block of code in a .htaccess file in /foobar/, your downloads should be in /foobar/download/ - these are the directories accessible by the paths mentioned from your webserver.

What we do is switch on FollowSymLinks which is required by mod_rewrite, if you don't need other options you can remove the +. We turn on the rewrite engine which is off by default, then set the base location for the URI rewrites.

The next two lines are our rewrite rules, if the request is for send.php (our script that counts downloads) we don't modify it, if we get a request for download/foo.bar that will become download/send.php?file=foo.bar for Apache (the rewrite base is prepended). The rule processed only filenames with extensions.

The download counter

<?php

$file = isset($_GET['file']) ? trim($_GET['file']) : '';

if (!$file) {
die("Error");
}

if ( substr_count($file, '..') > 0 or substr($file, 0, 1) == '/' ) {
die("Invalid filename.");
}

$path = dirname($_SERVER['PATH_TRANSLATED']) . '/' . $file;

if ( !file_exists($path) ) {
die("File not found: $file");
}

$ext = explode('.', $file);
if ( sizeof($ext) < 2 ) {
die("Invalid filename: should have extension");
}

We do some checking first, you should never display files to the visitors that they have requested without checking for unwanted characters like ../ or / at the start of the filename.

The $path's value is set to the directory containing our script + the filename requested. We then check if the file really exists and if it has an extension.

$ext = $ext[sizeof($ext)-1];

switch ($ext) {
case 'tgz' :
$type = 'application/x-gzip';
break;

case 'php' :
$type = 'text/html';
break;

default :
$type = 'text/plain';
}

header("Content-type: $type");

By default PHP sends a content type header of text/html to the browser so we need to modify it when this is not right. You should add more extension -> MIME type pairs if you serve different file types. We've sent text/html for PHP files because we want to present them syntax highlighted - our script is something like a download counter + PHP file browser.

Because we send a HTTP header there should be nothing sent to the browser before the last line of the block above. Output buffering can be used as a way around this but it's not needed here.

$fd = fopen ($path, "r");
$code = fread ($fd, filesize($path));
fclose ($fd);

switch ($ext) {
case 'php' :
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
<html>
<head>
<title><?php echo $file?> syntax highlighted</title>
</head>
<body>
<?php
highlight_string($code);
?>
</body>
</html>
<?php
break;

default :
echo $code;
}

This is the part which sends the file to the browser or presents the highlighted PHP file. The functions used are binary safe so you can send every type of files not only text.

require_once('../../config.php');
$db = db_connect();

$sql = "UPDATE download_file SET count=count+1 WHERE file = '$file' ";

$db->query($sql);
?>

And the final one, which actually counts the download. Include a file with our database info first - as you can see if opens a file which is out of the webserver root which makes it pretty safe. We connect to the database with our predefined function db_connect() which returns a PEAR::DB instance.

The query updated the download_file table, which holds the download files and the times they have been downloaded. We increase the count field by one for our file.

Note: Never make the mistake to first SELECT the count value, increment it in PHP and then write it to the database.

Author's URL: Martin Tsachev