QF setConstants/exportValue

Hi!

I am very  now:

I am doing a:

$this->setConstants(array('fID'=3D>''));
logfile($this->exportValue('fID'));

which is supposed to set fID to '' and after that write that in the =
logfile.
However the logfile does not show '' but something different. How can =
that
be?
The element exists (I even checked with elementExists)

What else can be wrong? How come I wonder again whether I got the
defaults/values/constants handling of QF?

Help would be highly appreciated!
Daniel