One thing that would be important to ensure accurate numbers is making sure the tracking image isn't cached. We should send back the following headers:
Cache-Control: private, no-cache, proxy-revalidate
So in core/Tracker.php, maybe do something like:
protected function outputTransparentGif()
if( !isset($GLOBALS[|| !$GLOBALS'DEBUGPIWIK') )
$trans_gif_64 = "R0lGODlhAQABAIAAAAAAAAAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==";
header('Cache-Control: private, no-cache, proxy-revalidate');
PHP ships with the default headers to not cache.
I agree we should probably set these headers explicitly (instead of assuming the default php configuration).
(In ) Fixes #646, setting cache headers explicitly to nocache instead of
assuming PHP default.