I'm having the exact same problem as the OP, TarasS, and RyanBr using Plesk 11.5 on CentOS 6.5 .
Oddly enough, I was able to get a new PHP install to work fine on a Plesk 12/CentOS 6.5 system, but the exact steps don't work for Plesk 11.5 .
I've read every post and supposed solution I can...