HHVM 4.80 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 4.56 (LTS) and HHVM 4.75–4.79 remain supported.
  • support has ended for HHVM 4.32 (LTS)


  • The bytecode cache can now store SystemLib units; this can lead to a better experience if HHVM is executed multiple times.
  • Clearer error messages for unresolved subtypes of mixed; prior versions can refer to the null or nonnull subtypes of mixed, which are more specific, but can be confusing.
  • Clearer error messages for variance mismatches: errors now say a type argument “only allows supertypes (it is contravariant”) or “must match exactly (it is invariant)”.
  • Fixed a caching bug when a source file appears to be modified, but the content (or bytecode) is unchanged, for example, by using touch; in prior versions, this leads to immediately exiting earlier, however the metadata should be updated to reflect the new modification time.

Breaking Changes

  • A typechecker error is now raised if the __LSB or __MemoizeLSB attributes are used in a final class. If this is raised, fix by removing the __LSB attribute, and replacing __MemoizeLSB with __Memoize.
  • Switch statements now throw if no case or default matches.
  • for loop conditions no longer permit comma-separated expressions. In prior versions, the behavior could be surprising - for example, in for(;foo(), bar();) {}, the return value of foo() is ignored. Commas are still permitted in other positions other positions, e.g. for ($i = 0, $j = 0; some_func($i, $j); ++$i, $++j).

Future Changes

  • The following runtime type warnings will be changed to raise errors in a future release. Initially, this will be done by changing the INI setting from 1 (warn) to 2 (error), and we then expect to remove the options entirely. Attempting to recover from these errors may lead to additional irrecoverable errors.
    • Upper bounds of generics: hhvm.enforce_generics_ub
    • Property type hints: hhvm.check_prop_type_hints