PHP7 extension documentation

Hi all, I'm one of the maintainers of BLENC PECL extension. I would like to port that extension to PHP7, and improve it a bit, making it compatible with other opcode caching extensions and adding some new features. The problem is that I cannot find any up to date documentation about Zend internals API and I don't have much time now to dig into the Zend code and try to figure out how the APIs should work. Is that possible that the latest good resource for implementing PECL extension is the "Extending and Embedding PHP (Developer's Library)" (from 2006)? It's 10 years ago. I'm a bit disappointed for this lack of documentation and that also stops me from trying to improve existing code. If you have some new resource, related to the latest PHP and Zend Internals please share it here. Thank you, Giuseppe Chiesa