6     Objects

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The object-oriented programming (OOP) paradigm has been around for many years now, although the degree to which it is support varies widely across languages. C++, for example, is object-oriented C, and, as some purists would say, implements more OOP functionality than even Java does.

Before PHP 5 came along, OOP support in PHP was quite flaky and more of a hack than a serious attempt. As a result the few that used it often regretted the choice, and it is not surprising that the whole system got a full rewrite in PHP 5 - it is now much more advanced and flexible, and should please just about everyone.

Topics covered in this chapter are:

• Objects and classes defined

• Class inheritance

• Access control

• Runtime type information

• Abstract and final properties and functions

• Constructors and destructors

• Magic functions

Chapter contents

6.1. Conceptual overview
6.2. Classes

6.2.1. Defining a class
6.2.2. How to design your class
6.2.3. Basic inheritance
6.2.4. Overriding functions

6.3. Objects
6.4. Variables
6.5. The 'this' variable
6.6. Objects within objects
6.7. Access control modifiers

6.7.1. Public
6.7.2. Private
6.7.3. Protected
6.7.4. Final
6.7.5. Abstract
6.7.6. Iterating through object variables

6.8. Object type information: instanceof and is_subclass_of()
6.9. Class type hints
6.10. Constructors and destructors

6.10.1. Parent constructors
6.10.2. Destructors
6.10.3. Deleting objects

6.11. Copying objects
6.12. Comparing objects with == and ===
6.13. Saving objects: __sleep(), __wakeup(), and get_object_vars()
6.14. Magic functions

6.14.1. __autoload()
6.14.2. __get()
6.14.3. __set()
6.14.4. __call()
6.14.5. __toString()

6.15. Static data
6.16. Helpful utility functions: class_exists(), get_class(), and get_declared_classes()
6.17. Interfaces: get_declared_interfaces()
6.18. Deferencing object return values
6.19. The Object-Oriented Website

6.19.1. A basic OOP site
6.19.2. A more complex OOP website

6.20. Summary
6.21. Exercises
6.22. Further reading
6.23. Next chapter