facebook 要终止支持php了，建议使用hhvm的应用迁移到php7。下面附上终止支持计划。

Ending Support for PHP

HHVM v3.30 will be the last release series where HHVM aims to support PHP. The key dates are:

• 2018-12-03: branch cut: expect PHP code to stop working with master and nightly builds after this date

• 2018-12-17: expected release date for v3.30.0

• 2019-01-28: expected release date for v4.0.0, without PHP support

• 2019-11-19: expected end of support for v3.30

Ultimately, we recommend that projects either migrate entirely to the Hack language, or entirely to PHP7 and the PHP runtime.

We expect support for real-world PHP code to break rapidly: for example, we are likely to replace reference parameters (&$foo) to builtins with inout parameters, make INT64_MAX + 1 === INT64_MIN (instead of a float), among other changes. In the short term, we expect it to be fairly straightforward to migrate code to deal with these changes, but this will require that any dependencies written in PHP are either forked and migrated to Hack, or migrated away from.

We’re extremely grateful to the users and developers of PHP, and are glad to have been part of those communities.