PHP 8.0 Likely To Have A New JIT Engine
PHP 8.0 is still out in the distance with PHP 7.1 being what's under development now for release in the weeks ahead while PHP8 is much further down the road. However, Zend has already begun work on a new JIT for PHP that they hope will be able to "deliver some useful results" for the next major PHP version.
As of last month when announcing the project, they aren't yet at a stage for delivering real performance improvements but do have the JIT infrastructure working on Linux x86/x86_64. The JIT code generator aims to be minimal and simple while they are still researching and testing different design approaches.
More details via this mailing list post. In case you missed it from last month is also other talk about possible changes for PHP 7.2 and PHP 8.0.