Familiarity with compilers would be a plus.
* Understand strengths/weaknesses of the JIT, and whether it may be useful for your application
* Understand how a modern JIT compiler works under the hood
Nikita Popov is a long-time PHP core contributor, now working at JetBrains, who is behind many major language features like generators, typed properties and arrow functions. Nikita also maintains the PHP-Parser library and contributes to the LLVM toolchain.