Dropping support for php 7.1 and older?

[TysonAndre]

@nikic - What are your thoughts on dropping support for php 7.1 and older after releasing 1.0.10 - this would simplify the implementation a bit (stubs, ast coercion logic on PHP_VERSION_ID, etc) and reduce the amount of testing

[nikic]

Yeah, I think it's fine to drop support for PHP <= 7.1.

[TysonAndre]

This was done in #185 , along with deprecating ast versions 50 and 60