I do this:
<body>
<!– mfunc –>
$visitors_online = new usersOnline();
$currentlyonline = $visitors_online->count_users();
<!–/mfunc –>
…
</body>
But it’s just showing a blank page.
I was just about to ask the same question… I can’t find anything in the FAQ about fragment caching and how to set it up. Got a mail from Frederick saying that it is possible.