The 0.9.x versions will be tracking syntax from PHP versions 7.1.x and are runnable on PHP 7.1+. Please use version 0.8.x if you're using a version of PHP < 7.1.
See the file NEWS for what has changed in this version.
Future releases (0.8.8+, 0.9.6+, 0.10.0+, etc.) will be published to phan/phan instead of etsy/phan on packagist.
If you are using phan 0.9.x, it's recommended to switch to phan 0.10.y releases
(0.10.x depends on php-ast 0.1.5+ for AST version 50).
Phan 0.9.x will be supported for only a few more patch versions.
(and Phan 0.8.x will switch to AST version 50 after that)