Change effective on 16 November 2015
The ability for PHP applications to concurrently install the PHP and HHVM runtimes by specifying version selectors for both the “php” and “hhvm” packages in
composer.json is now deprecated.
In a future update, the behavior will be changed to only install an HHVM version that satisfies all requirements in
composer.lock (HHVM internally identifies itself as PHP version “5.6.99”).