Description:
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Apc/u is (obviously) a good and fast way of sharing data between aplications
(as intended), but sometimes you may need NOT to do it, at least not
in the 'normal way'...

I often manage several websites in a dev enviroment, and the 'worst'
thing one could do is to store sensible data like sessions, user data,
etc... (without a Prefix) to avoid extra connections to the database...

apc_store('user_{id}', [session_data => ..., etc => ...])

Then all the dev websites will share the exact same info/data for the user_{id}
Of course I have a wrapper class that prefix everything but I think will be very
very usefull to have it implemented in the core and because C is faster...
A simple function that set the prefix for the session, for instance...

apcu_prefix(string $prefix = null)

And calling the function without argument can return the current prefix
or maybe just reset it to default...

Can also be a very important feature from a security POV since I have seen
some very bad configured shared hosts having this problem, and one could
read the info that other hosts had stored...

The prefix can also act like a password... for functions like apcu_cache_info
Only if you know the prefix/password you will be able to get the info

Thank you