HHVM 4.25 is released! This release marks the end of support for 4.19; 4.20-4.24 remain supported, as do the LTS releases 3.30 and 4.8.

Highlights

Corrected stack trace file names and line numbers for inlined functions; previously, the file name and line number from the first non-inlined frame would be used instead.
It is no longer a type error for a disposable to implement a non-disposable interface.
@param documentation is now shown in IDE signature help.

Breaking Changes

The getAttributeRecursive and getAttributesRecursive reflection methods have been removed; they were previously marked as __Deprecated.
Many functions and methods have had their by-ref parameters replaced with inout parameters:
- natsort(), natcasesort(), sort(), rsort(), asort(), arsort(), ksort(), krsort(), usort(), uasort(), and uksort()
- array_pop(), array_push(), array_shift(), array_splice(), array_unshift(), and shuffle()
- IntlTimeZone::getOffset()
- pagelet_server_task_result(), xbox_send_message(), and xbox_task_result()
call_user_method() and call_user_method_array() have been removed - they have been deprecated since PHP4.
the runtime no longer recognizes the aliases double, real, integer, and boolean; use float, int, and bool instead. These aliases were previously typechecker errors.
Added return types to many Async MySQL methods; this may lead to new type errors.

hhast-migrate --ref-to-inout can be used for many of the reference-to-inout changes.

references will be completely removed from the language and runtime; we will be publishing details in a separate post.