$remove = array_diff($old_cat, $new_cat);print_r($remove);$sql = "DELETE FROM apparel_categories WHERE apparel_id=\"{$_POST['id']}\" AND category_id=\"$remove[]\""; $deleted = mysql_query($sql); if(!$deleted){ throw new Exception("While saving category (-), you got a mysql error: ".mysql_error($db)."<br>\$sql was:".$sql.'');}$add = array_diff($new_cat, $old_cat);print_r($add);$sql = "INSERT INTO apparel_categories (apparel_id, category_id) VALUES (\"{$_POST['id']}\", \"$add[]\")"; $added = mysql_query($sql);if(!$added){ throw new Exception("While saving category (+), you got a mysql error: ".mysql_error($db)."<br>\$sql was:".$sql.'');}