filesize() Problem: better description:

Hi it´s me again with a better decription:
the following script checks the size of a file, adds something to the file and then checks the filesize again.
The Problem: it´s both the same size, but this actualli can´t be. How do I get the real size after the adding?
See the error also at: http://www.seeagency.de/t.php3

$file = "test.txt";

$size=filesize($file);
echo $size."n<br>n";

$addtext="This text will be addes to the file!!n";

$open=fopen($file, "a");
fputs($open, $addtext);
fclose($open);

$size=filesize($file);
echo $size;

thanks a 1000 times,
Kai Seefeldt

I found the solution:
clearstatcache();
Thanks!