HHVM

Definitions

1. The HipHop Virtual Machine, an open-source virtual machine created at Facebook that executes PHP and Hack code with just-in-time compilation. It succeeded HipHop for PHP, a 2010 project that translated PHP into C++ and compiled it ahead of time, which delivered large speedups but made development slow and diverged from PHP's runtime behaviour. HHVM replaced that approach around 2013 by compiling code to bytecode and then to machine code at runtime, using observed types to generate faster paths. Its performance pressure is widely credited with pushing the PHP project toward the major speed improvements in PHP 7. Facebook introduced Hack in 2014, a gradually typed dialect of PHP that runs on HHVM, and from HHVM 4.0 in 2019 support for PHP itself was dropped so the runtime could evolve with Hack alone. HHVM now serves mainly Meta's own codebase and the small community using Hack.

   In plain English: Facebook's faster engine for running PHP code, which compiles it on the fly instead of interpreting it line by line, eventually leading to a whole new programming language called Hack.

   Example: "Facebook built HHVM because standard PHP was too slow for a billion users, then basically forked the language into Hack."

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