Merge pull request piotrplenik#121 from peter-gribanov/version_announce

Announce PHP version

Author: Tomáš Votruba

README.md

@@ -57,6 +57,8 @@ years of collective experience by the authors of *Clean Code*.
 
 Inspired from [clean-code-javascript](https://github.com/ryanmcdermott/clean-code-javascript)
 
+Although many developers still use PHP 5, most of examples in this article work with PHP 7.1+.
+
 ## Variables
 
 ### Use meaningful and pronounceable variable names