HHVM 4.147 is released! This release marks the end of support of 4.139; 4.140, and 4.143 - 4.146 remain supported, as do the 4.102 and 4.128 LTS releases. 4.141 and 4.142 were cancelled due to the holiday season.


  • Add coeffects to thrift_protocol_set_compact_version, DateTime and mbstring functions.
  • Support hover and go-to-definition on type parameters in an IDE.
  • Support hover and go-to-definition on the abstract keyword in an IDE.

Breaking Changes

  • The result of HH\FIXME\UNSAFE_CAST is now considered readonly if the input is readonly.
  • Always raise an error when inheriting members that differ only by case (previously the error would be raised only if case_sensitive_inheritance option is enabled)