For more than 10 years, PHP core developers repeatedly raised the topic of providing a formal language specification for PHP. Now a team of facebook employees has written such a specification. The spec document is currently only available as a preview chapter a preview chapter . PHP veteran Sara Golemon announced on the “PHP internals” list that the full document will be ready for O’Reilly’s OSCON 2014. Sara Golemon published the standard book on “Extending and Embedding PHP” some years ago and now works for Facebook’s own PHP implementation HHVM. The PHP spec defines PHP version 5.6 in about 200 pages and contains all the odd and obscure quirks of the language core. Facebook’s own HHVM aims to be as close to the spec as possible. Currently, PHP developers discuss how amending the spec can become a mandatory part of the language development process. Though some are sceptic that all developers will embrace the change in the process, everybody on the list was happy to have the new document.

Software Architect Stas Malyshev:

Thank you Sara and Facebook team for doing something we’ve been talking
about for more than a decade and before that nobody actually attempting
to do. I think it is a great development and I hope to see the first
version soon.

http://dl.hhvm.com/resources/PHPSpec-SneakPeak.pdf