The select part is simple - you are not asking for the subcategories to be displayed:

explode(",",'81,69,156,66')

This will display top categories 81, 69, 156 and 66, but you also need to specify all of their subcategories individually.
PHP Code:
explode(",",'81,81_199,81_200,81_203,69,69_177,69_178,156,156_235,156_236,66,66_212,66_213') 
The code could be reworked to do this automatically, but I didn't get into that at the time since the original code worked.