This document lists some resources people may find useful to start to learn how PHP works internally, and what is involved in PHP extension development.
www.phpinternalsbook.com is a collaborative effort between several developers of the PHP language to better document and describe how PHP works internally.
The three primary goals of the book are:
- Document and describe how PHP internals work.
- Document and describe how to extend the language with extensions.
- Document and describe how you can interact with the community to develop PHP itself.
Thomas has put together a comprehensive set of example of how to implement many different features in a PHP extension.
Each of the examples are in a separate branch, so you can see precisely the work needed to add that particular feature.
https://github.com/ThomasWeinert/php-extension-sample
PHP 7 Virtual Machine by Nikita Popov