How to get started with OOP in PHP. Inspiration from Codecourse.
http://code.tutsplus.com/tutorials/object-oriented-php-for-beginners--net-12762
http://codeumbra.eu/object-oriented-programming-with-php-5
https://da.wikipedia.org/wiki/Paradigme
https://en.wikipedia.org/wiki/Programming_paradigm
https://da.wikipedia.org/wiki/Scrum
http://php.net/manual/en/language.oop5.php