Searching through my bookmarks, only links I found are those :
- Extension Writing Part I: Introduction to PHP and Zend
- Extension Writing Part II: Parameters, Arrays, and ZVALs
- Extension Writing Part II: Parameters, Arrays, and ZVALs [continued]
- Extension Writing Part III: Resources
- Wrapping C++ Classes in a PHP Extension
If you are really interested by the subject, and ready to spend some money on it, you could buy the book Extending and Embedding PHP (some pages are available as preview on Google Books too) ; I’ve seen a couple of times that it was the book to read when interested on this subject (In fact, I’ve just bought it ^^ didn’t have the time to read it yet, though 🙁 ; the first pages seem OK…)
BTW, the author of that book is also the author of the first four articles I linked to 😉