This first incarnation of object-oriented programming (OOP) support covered only the barest implementation of object-related characteristics. In the words of one core developer, "A PHP4 object is just an Array with some functions bolted onto the side." It is this generation of PHP objects that you'll explore now.
With the second major release of the Zend Engine (ZE2) found in PHP5, several new features found their way into PHP's OOP implementation. For example, properties and methods may now be marked with access modifiers to make them inaccessible from outside your class definition, an additional suite of overloading functions are available to define custom behavior for internal language constructs, and interfaces can be used to enforce API standards between multiple class chains. When you reach Chapter 11, "PHP5 Objects," you'll build on the knowledge you gain here by implementing these features in PHP5-specific class definitions.
The PHP Life Cycle
Variables from the Inside Out
Setting Up a Build Environment
Your First Extension
Working with Arrays and HashTables
The Resource Data Type
Startup, Shutdown, and a Few Points in Between
Diverting the Stream
Configuration and Linking
Setting Up a Host Environment
Appendix A. A Zend API Reference
Appendix B. PHPAPI
Appendix C. Extending and Embedding Cookbook
Appendix D. Additional Resources