5.3 is the one most will have.

Just check the version in most standard repos and you have your answer, far more accurate than asking a random small sample of people.

http://mirror.centos.org/centos-6/6/...6_3.x86_64.rpm
http://packages.debian.org/stable/php5
http://packages.ubuntu.com/precise/php5

and so on. no need for a public poll to find out.
JmZ Reviewed by JmZ on . PHP Version Answer :P Rating: 5