Full On Design

Here is a really easy and lightweight way of logging the amount of downloads.

<?php # File created on 25th April 2009 by Mike Rogers (http://www.fullondesign.co.uk/). 

## Start defining constants ##
define(LOG_URL, '/home/user/download_logs/'); // Put the location of where you want to put the logs. Make sure this is absolute
# $_GET['ID'] - this is the ID of the file we want. It gets the value from the URL.

## Now set the data you wish to use - this can be moved to an include if you want ##
$file[0] = 'http://www.example.com/file.pdf';

## Define the functions required to update the file.
function update_file($filename, $value){
	if(is_writable($filename) && is_readable($filename)){
		if(file_put_contents($filename, $value)){
			return TRUE;
		}
	}
	return NULL;
}
function pull_file($filename){
	if(is_writable($filename) && is_readable($filename)){
		return file_get_contents($filename);
	}
	return NULL;
}
function rebuild_file($filename){
	if(is_writable($filename) && is_readable($filename)){
		file_put_contents($filename, '1');
	}
}

if(is_numeric($_GET['ID'])){ // Meaning the Data sent is safe.

	// Build log file URL
	$filename = LOG_URL.$_GET['ID'].'.log.txt';
	$value = pull_file($filename);

	header('location:'.$file[$_GET['ID']]);

	// Update logs
	if(is_numeric($value)){
		update_file($filename, ($value+1));
	} else { // Meaning the file does not exist or has been messed with.
		rebuild_file($filename);
	}
} else {
	echo 'Sorry, there was an error.';
}

/* If you want to see how many people have downloaded a file, run something like:
# pull_file(LOG_URL.numberishere.'.log.txt');
/*

You are free to share, modify and use this code for commercial uses. Please give a link back (to http://www.fullondesign.co.uk/ ) if you can, but you don't have you.

I claim no liability for this code, you use it at your own risk.

*/

?>

You can run this by changing the URL that accesses the file. For example:
file.php?ID=0

Feel free to edit and share this code.