HHVM 4.98 is released! This release marks the end of support for 4.92; HHVM 4.93–4.97 remain supported, as do the 4.56 and 4.80 LTS releases.


  • Minor improvements to various typechecker error messages.

Breaking Changes

  • The typechecker now correctly reports errors when a class inherits multiple conflicting definitions of the same non-abstract constant from its parent class/interfaces/traits. These had already been runtime errors, but previously wouldn’t be caught by the typechecker.

Future Changes

  • We expect the built-in function inst_meth to be removed in a future release (anonymous functions or meth_caller can be used instead).
    • The .hhconfig flag disallow_inst_meth=true and the INI option hhvm.hack.lang.disallow_inst_meth=true can be used to enforce the future behavior now.
  • As mentioned last week, we expect string concatenation ('hello '.$name) and interpolation ("hello $name") to become restricted to string and int values in the future.
    • This release adds the runtime (INI) option hhvm.notice_on_coerce_for_str_concat which can be used to raise a notice (if set to 1) or throw an InvalidOperationException (if set to 2) when concatenating/interpolating other types, in addition to the typechecker flag added in last week’s release.