Newb question : What package will the system use if both testing and unstable sources are defined ?

[Maxim Vexler <hq4ever@gmail.com>]

Hello.

I'm facing this situation on my first day with debain :

I wish to have both php5 and xorg-server installed on my system, those
packages are provided from the unstable repository - which is fine.
The problem arises with my understanding of the way apt works: If a
version of a package FOO is available both in testing and unstable
repository's which version will apt use ?
What if I wish it to pull only the php5 package from the unstable
repository but have the rest of the system installed from the testing
tree -- it that configuration possible?


Thank you.

--
Cheers,
Maxim Vexler (hq4ever).

Do u GNU ?