Hi,
from what I've read here and there, most of the time,
it's not usefull.
The idea is that at the end of the script, ressources will be cleared anyway.
But I suppose it can be usefull IF you're opening a lot of
connections during the execution of your PHP script (so, before its
end).
In that situation, releasing things when they are no more needed
might be usefull (also an ISP may appreciate you don't eat
too much ressources with your PHP script, if your server is
crowded by many users)
Hervé.