When one of two forums is getting too much traffic perhaps one has become too specific. This is the crux of my suggestion - I'm not married to any specific name idea. But I think it would be healthier to rebalance the two's volume. That might involve renaming both forums, with the main forum perhaps being
'PHP - Beginner & Novice Discussion' This forum is for when you are just starting out.
And then this forum being
'PHP - Advanced Discussion' This forum is for when you've moved to building your own pages from scratch or using major frameworks such as Joomla, CakePHP, etc.
There is the danger of over balancing though and causing this forum to become the busy one. Also, that is a grayer line. The problem with a line that is too fine is people will post in both forums.