If you are starting with good practices in PHP I would like to recommend the PHP design patterns it is awesome. The book start with a short introduction in Object Oriented Programming , UML and the concepts of Design Patterns.
The book divides in three sections the patterns, the creational patterns, structural patterns and Behavioral patterns. Inside of each section is compound of two patterns and the list bellow explain to us which are they.
As a plus section in the book the author show to us how to use the Proxy Pattern with MySQL, however, you can use with any database.