Some links to reading material on OO PHP

http://code.tutsplus.com/tutorials/object-oriented-php-for-beginners–net-12762

http://knowpapa.com/procedural-to-oop/

http://www.davegardner.me.uk/blog/2010/11/21/why-you-should-always-use-php-interfaces/

Defining relationships in databases

http://blog.andreasartori.me/defining-relationships-among-database-tables-with-eloquent/