My first experiments with object-oriented programming in PHP took place about six years ago. Unfortunately, the book that introduced me to the subject concentrated on the mechanics of writing classes and paid little heed to principles underlying OOP. As a result, I wrote classes that were closely intertwined with a specific project ( tightly coupled, to use the OOP terminology). Everything worked exactly the way I wanted, but the design had a fundamental flaw: the classes couldn t be used for any other project. Worse still, it was a large project a bilingual, searchable database with more than 15,000 records so any changes I wanted to make to it involved revising the whole code base. The purpose of this book is to help you avoid the same mistake. Although most chapters revolve around mini-projects, the classes they use are project-neutral. Rather than being a how to cookbook, the aim is to help developers with a solid