HHVM was originally created as an alternative to PHP for demanding and high-traffic sites. Due to performance issues with PHP the team at Facebook developed the HipHop Virtual Machine (HHVM). It is a system that uses just-in-time (JIT) compilation to convert PHP code into a machine language to establish a synergy between the PHP code and the underlying hardware that runs it.
Many high-traffic sites at Kinsta have utilized HHVM over the years and have seen dramatic decreases in load times. HHVM also enables object caching, which is an internal caching system that was introduced by WordPress to store data from the database in PHP memory. This increases database efficiency by reducing the number of database calls and speeds up PHP execution times. HHVM is great for dynamic parts of your WordPress site that might not be cacheable.
With all that being said, HHVM is no longer a stable or suitable solution for high-traffic WordPress sites. HHVM, in fact, was never officially supported by WordPress. And as of May 2017, it’s also no longer a part of WordPress core’s testing infrastructure. This has introduced bugs and compatibility issues (which we have seen first-hand) with recent versions, including third-party plugins and themes.
Beyond support for HHVM hosting, our PHP vs HHVM benchmarks showed that PHP 7.2 actually performed faster than HHVM. This included tests of a standalone WordPress site, WooCommerce, and Easy Digital Downloads.
Due to the fact that HHVM is no longer being supported or tested with WordPress, and in some configurations is actually slower, we recommend using PHP 7.2. We offer PHP 5.6, 7.0, 7.1 and 7.2 in the MyKinsta dashboard. You can easily switch back and forth with a click of a button.