rolling hit counter script?

[deko]

I use this script to keep count of visits to my site - it's on every page in the
site.

<?php
$file = '/home/post/public_html/viscount';
if ($counter = @file ($file)) {
$line = each($counter);
if (!$counter) {
$counter = 1;
} else {
$counter = $line[value]+1;
}
}
$fp = fopen ($file, "w");
fwrite ($fp, "$counter") ;
fclose($fp);
?>

But how to maintain rolling hit counter? For example:

292 visits in the last 24 hours
3,841 visits in the last 30 days
50,389 visits in the last 365 days

Let's say I want to update these stats every 3 hours - I have a cron job that
runs at 00:00, 03:00, etc. And I have the following files:

viscount - number of hits in current interval (3 hours)
viscount_prev - number of hits in previous interval
viscount24 - number of hits in last 24 hours
viscount30 - number of hits in last 30 days
viscount365 - number of hits in last 365 days

So, at each interval, a script copies (overwrites) viscount to viscount_prev.
Then subtract viscount_prev from viscount and add result to viscount24,
viscount30 and viscount365?

Has anyone done something like this before? Can you point me to a sample
script?

Thanks in advance.