HHVM 4.49 is released! This release marks the end of support for 4.43; HHVM 4.44–4.48 remain supported, as do the 4.8 and 4.32 LTS releases.


  • New .hhconfig option disable_modes (previously disable_partial) will cause the typechecker to treat all files as strict (comments after <?hh no longer have special meaning).
    • The default value will be false for the foreseeable future.
  • New hackfmt flag --format-generated-code can be used to format generated and partially generated files.
  • Fixed a bug that could cause part of hackfmt output to be missing when formatting partially generated files, and other minor fixes and improvements for hackfmt.
  • Fixed a bug that could prevent the “go to type” IDE feature from working inside async functions.
  • Improved various typechecker error messages, e.g. when accessing an optional shape field it now recommends using Shapes::idx instead of ??.

Breaking Changes

  • Comparing (<, >, <=, >=, <=>) a legacy PHP array with a non-array now throws InvalidOperationException (previously only raised a Notice). It had already been a typechecker error.
  • It is now a runtime error if class_meth is used with arguments that are not a ::class and a string literal (a string literal as the 1st argument will also not cause a runtime error, but ::class literal is recommended). It had already been a typechecker error.
    • If a dynamic pointer is required, annotate the method with <<__DynamicallyCallable>> and use HH\dynamic_class_meth().

Future Changes

  • We are working towards deprecating (and eventually removing from the language) “magic methods” such as __call or __get. Currently, you can use the INI option hhvm.no_use_magic_methods=true to trigger warnings whenever a magic method is invoked, e.g. when an undefined method is called on a class that has the __call magic method.
  • Comparing Hack arrays to true, false, and null with the “fuzzy” equality operators (==, !=) will be changed so that non-empty Hack arrays are == true and empty Hack arrays are == false and == null.
    • The INI option hhvm.hack_arr_empty_based_bool_eq_cmp=true can be used to enable this behavior now.
    • The new behavior is consistent with legacy arrays, making it easier to migrate to Hack arrays.