Okay Question Number 3.

My Bestsellers sidebox is giving me this error

Code:
[16-Dec-2012 13:37:51] PHP Fatal error:  Can't use function return value in write context in testing.franktonmodels.co.nz/includes/modules/sideboxes/radiocontrol/best_sellers.php on line 47
and line 47 is

Code:
cat_filter($best_sellers_query) .= $limit;
Just sorting out the little bugs :) Thanks for any help guys!