The problem lies in blesta trying to use php include path, but the include path which is default for CentoOS does not have proper permissions, so, you have to force a path with a proper permission in there and IT WILL WORK.
I don't know what blesta is doing but i suspect it uses RSA to decode something and php is trying to put this into the session path, which not having the correct permission will not work and then php will throw an error in the RSA.
I repeat this so it's clear, Centos will NOT work on the default path, you have to manually include the path as I stated and it will work. I tried this 5 times in a row on a new VPS just to be sure it was this and I confirm it once again now.
Solution:
Put this into /etc/php.ini
include_path = /usr/share/php
make sure the directory has correct permissions and restart php and installer should work properly.
