Add "Clean Code PHP" book (#4064)

free-programming-books.md

@@ -2118,6 +2118,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### PHP
 
+* [Clean Code PHP](https://github.com/jupeter/clean-code-php)
 * [PHP 5 Power Programming](http://www.informit.com/content/images/013147149X/downloads/013147149X_book.pdf) (PDF)
 * [PHP Best Practices](https://phpbestpractices.org)
 * [PHP Internals Book](http://www.phpinternalsbook.com)