HHVM (aka the HipHop Virtual Machine) is a virtual machine designed for executing programs written in Hack and PHP. It uses a just-in-time compilation approach to achieve superior performance while maintaining the flexibility that PHP developers are accustomed to. To date, HHVM (and its predecessor HPHPc before it) has realized over a 9x increase in Web request throughput and over a 5x reduction in memory consumption for Facebook compared with the PHP 5.2 engine + APC. HHVM should be used together with a FastCGI-based Web server like Nginx or Apache.
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