Count a group's website visits

I use my webserver's logs to count visits to my website.

The software "Webalizer 2" displays these data in plain form with some diagrams.

But now I want to count visits by a special group of users separately. I have premium users and standard u开发者_如何学运维sers. For premium users I want to have a separate statistics page so that I can see how many premium users' hits there are.

How can I achieve that?

In my PHP script files, I detect the status as follows:

<?php
if ($_SESSION['status'] == 'premium') {
  // do something here
}
?>

The easiest way would - of course - be to have a MySQL update statement there to increment the premium users' counter.

But that would also be a lot of database traffic. So I would prefer another solution.

I thought I could show a 1x1 pixels .gif image to the premium users. Then I could check the webserver's statistics for the file "counter.gif". BUT: I guess the client will cache the graphics file so my results won't be correct, right?

Do you have an idea how to implement such a counter?

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There are many solutions to this problem...

If you use a 1x1 pixel gif and are worried about caching, do something like this:

<img src="counter.gif?t=<?php echo time(); ?>" alt="" />

But then you'd still have to have some tool on the backend to track, and then analyze this data.

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Alternatively Google Analytics has created simple ways to do this. Assuming you're already using their tracking code, you can add a Custom Variable. See more here:

http://code.google.com/apis/analytics/docs/tracking/gaTrackingCustomVariables.html#visitorLevel

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An alternative to a database solution, could be something like adding a query string to the url for the premium users like:

?user=premium

And register the different urls with for example Google Analytics, but I don't know if your site structure allows for that.