BuddyPress.org

4,42,46 is not an array, that is a string of ids separated by commas. You should not be imploding the ids.

Get rid of this part of your function:

if(!empty($excludecats)){

$excludecats = implode(',',$excludecats);

}

You should read up on arrays http://php.net/manual/en/language.types.array.php