[RFC] Union Types

As alluded to in an earlier email today[1] I am now moving the Union Types RFC[2] to the discussion phase. The short summary of the RFC is that it permits a type declaration to be one of several enumerated types. For example, this is a potential signature for a multi-type map routine: function map(callable $f, Array | Traversable $iterable); The second parameter $iterable is required to be of type Array or Traversable - any other type will error. I look forward to a helpful and meaningful discussion! [1]: http://news.php.net/php.internals/92252 [2]: https://wiki.php.net/rfc/union_types