Minimum PHP version

[pedzed]

What is the minimum PHP version being supported?

I propose 5.5, because 5.3 is EOL and 5.4 is in its extended (security) support, which ends in 14 Sep 2015.

https://secure.php.net/supported-versions.php
https://secure.php.net/eol.php

The minimum version should be added to the README so users will know.