This books is a great reading to deep your knowledges in core level of PHP, to understand how PHP works, how it process data and how code should be structured to achieve good optimization. This book is primarily targeted at developers who have experience in the C programming language. However, where-ever possible authors attempt to distill the information and summarize it so that developers who don’t know C well, will still be able to understand the content.


There are three primary goals of this book:

  • 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.


This book devided by three main parts: Internals of PHP5, Internals of PHP7 and Testing PHP Source. We would suggest you to read articles one after another including internals of PHP5 in spite of the fact that the LTS version of PHP5.6 will not be supported anymore since January 1, 2019.

Particular attention in the book is devoted to the peculiarities of the work of PHP7, specifically, such topics as:

  • How to build PHP extensions and PHP from sources
  • Internal types, such as zvals, string managment, hashtables, resources and functions
  • Learning the PHP lifecycle
  • Extension skeleton
  • Registering and using PHP functions
  • Declaring and using INI settings
  • ZEND extensions
  • Memory management and its debugging
  • Zend engine

TL;DR: Conclusion

This book is completely free and open to be modified, so if you want to share your knowledges you could contribute to GitHub repository. Or vice versa, if you want to deepen your knowledge of how PHP works at a low level, this is the book you should pay attention to.