icu upgrade (for php purposes) during php upgrade

icu upgrade (for php purposes) during php upgrade

I am experiencing a cascade problem in upgrading my server.
Context: I want to create multiple version of php on my server, and
particularly add the newest version (5.5.2). I have to be careful, as I am
hosting websites in production state. I don't want to mess up with php!
Issue: I am asked to get icu 4 or more, and I only supply icu 3.6.
configure: error: ICU version 4.0 or later is required
I tried to compile from source (downloaded/tar-ed/ configured and ran make
and make install). I couldn't see any error during this installation.
However, my system seems to be still featuring icu3.6.
Question: Do you guys have an idea how to upgrade an icu version properly?
My guess is that, as I am not instaling icu from scratch, there is some
block while. I couldn't find exhaustive upgrade checklist on the official
website or on the web.
As an accessory question, should I expect any other dependancy issue that
you would have had knowledge of?
Thanks a lot in advance
Cheers