HHVM 4.56 is released! This release has long term support, so:

  • this release will be supported for approximately 48 weeks
  • the next LTS will be released in approximately 24 weeks
  • HHVM 4.32 (LTS) and HHVM 4.51–4.55 remain supported.
  • support has ended for HHVM 4.8 (LTS)

Additionally, 4.56 is the last release with support for several older Linux distributions and MacOS versions. In particular, we expect this to be the last release with support for Ubuntu 16.04 (Xenial), Debian 8 (Jessie), and Debian 9 (Stretch). See ‘Future Changes’ below for details.


  • apc_fetch() expiration is now deferred until the end of the first request that sees an expired result; this request will return false, but any concurrent requests will see the old value until the first request has finished. This change aims to reduce ‘thundering herd’ problems when many requests simultaneously attempt to refresh a hot key.

Breaking Changes

  • \HH\INCORRECT_TYPE<T> has been removed from the HHI definitions.
  • Support for __get, __set, __isset, and __unset has been removed from HHVM and the parser. Builtin classes that used these with fixed property names have a new native implementation.
  • The Redis extension has been removed. This extension contained no native code, so can be extracted from past versions of HHVM and updated as a standalone library if required, though we do not support this usage.

Future Changes

As announced in November, we are changing our distribution support lifecycle, starting with nightly builds and the next release:

  • MacOS: we aim to support the latest stable release - currently Catalina. When a new version of MacOS is released, we plan to support both for 6 months.
  • Debian: we aim to support Debian stable. When a new version is promoted to stable, we plan to support both for 6 months.
  • Ubuntu LTS: we aim to support the current LTS release (20.04); when a new Ubuntu LTS is released, we plan to support both for the next 6 months.
  • Ubuntu ‘interim’ releases: we plan to support these for 9 months, matching the length of time they are supported by Canonical.

As long as dependencies are available from official upstream repositories, we plan to package x.y.z releases for any Linux distributions where we packaged x.y.0; we also aim to do this for MacOS as long as the versions are available from our build infrastructure provider.

Concretely, this means that we no longer commit to supporting:

  • Debian 8 (Jessie)
  • Debian 9 (Stretch)
  • Ubuntu 16.04 (Xenial)
  • MacOS 10.14 (Mojave)

We will generally keep building packages for distributions we no longer support as long as they keep working and they do not hold back development. That said, starting with 4.57, we are immediately ending support for distributions that include GCC6 or below:

  • Debian 8 (Jessie)
  • Debian 9 (Stretch).
  • Ubuntu 16.04 (Xenial)

Other unsupported distributions may be removed from future releases without further notice.