Thanks! Worked perfectly. 
Thanks for the suggestion. It didn’t fix what I am trying to do.
Basically, while the php is executing the while ( bb_forum() ) : loop, I need to check the current forum against the forum it is writing to the menu.
If there are 4 forums in the while loop, I need it to check the current forum id against each forum id as it is writing it to html. If the current forum id matches the forum id it’s writing, then it would add the class="on" attribute to the li tag.
