What is HHVM?
HHVM is an open-source virtual machine designed for executing programs written in Hack and PHP. HHVM uses a just-in-time (JIT) compilation approach to achieve superior performance while maintaining the development flexibility that PHP provides.
HHVM supports Hack, PHP 5 and the major features of PHP 7. We are aware of minor incompatibilities, so please open issues when you find them. HHVM also supports many extensions as well.
HHVM Features
- The Hack Language
- JIT Compilation
- HNI
- Proxygen and FastCGI support
hphpd
debugger- ... and more
The JIT Compiler
Rather than directly interpret or compile PHP code directly to C++, HHVM compiles Hack and PHP into an intermediate bytecode. This bytecode is then translated into x64 machine code dynamically at runtime by a just-in-time (JIT) compiler. This compilation process allows for all sorts of optimizations that cannot be made in a statically compiled binary, thus enabling higher performance of your Hack and PHP programs.