Change effective on 24 May 2018
The following new runtime versions are now available for PHP applications:
The following PHP extensions have been added or updated:
ext-blackfire, version 1.20.0
ext-newrelic, version 188.8.131.52
An issue has been fixed that could cause PHP-FPM to crash on the heroku-18 stack.
The default runtime on the heroku-18 stack is now PHP 7.