Currently PHP developers face a great problem with PHP version - most OS repos already have outdated versions (CentOS has 5.4 which has passed its end of life!), but just swapping out versions is just not an option - especially with the version requirements of different frameworks / libraries. Furthermore, usually to have more than one version meant recompiling, and keeping up with updates - and no one wants that. Here's how to setup a server (virtual of physical), with ISPConfig3 hosting panel, multiple PHP versions, latest Apache and Mariadb in less than a half hour, with zero compiling. You can then manage your virtual hosts and their PHP version from a nice UI.
I recently tried moving from MySQL to MariaDB, and was truly surprised with the results - everything works just fine, didn't even have to recreate users/databases. Well, everything except Redmine (and I would assume, and other Passenger app).