Since some of the websites I host on my vServer need a PHP version > 5.3 I had to setup an environment that allows to choose PHP version seperately for every vHost.
The following steps did the trick for me on CentOS 6.7 / Plesk 11.5 (hosted with 1blu.de).
First we need to setup the atomic repository which contains multiple PHP versions and tools for dealing with them in Plesk:
wget -q -O - http://www.atomicorp.com/installers/atomic | sh
After this we have to install plesk-php-panda:
yum install plesk-php-panda
Now we should be able to choose a different PHP version for every vHost. Just go to the hosting settings of your domain and choose the PHP version that fits your needs: