Core PHP Programming, Third Edition

6.15. The Evolution of the Zend Engine

For the rest of this chapter, Zeev discusses the object model introduced in Zend Engine 2, especially with regard to how it differs from earlier object models in PHP.

When we implemented PHP 3, PHP/FI's replacement, back in the summer of 1997, we had no plans for object-oriented capabilities. It got pretty far without having any notion of classes or objects. It was to be a purely structured language. However, class support was added to the PHP 3 alpha source tree on the night of August 27. Adding a feature to the language at that time required little discussion because few people had discovered PHP. Starting August 1997, PHP made the first step toward becoming an object-oriented–friendly language.

Indeed, ...