The version of CMake which comes with CentOS6.3 is too old for the latest HHVM which requires CMake version >= 2.8.7. Either find another RPM from a nearby distro, or try using @jackywei's instructions for installing CMake 2.8.10.2 from https://github.com/jackywei/HOW-TO-BUILD-HHVM-WiKi/wiki/Build-&-Install-CMake-2.8.10.2-in-CentOS6.3