Represents an entity that can be iterated over using foreach, allowing a key, except it does not include objects that implement KeyedIterator nor Set and ImmSet

The iteration variables will have a type of Tk for the key and Tv for the value.

In addition to Hack collections, PHP arrays are KeyedContainers.

Interface Synopsis

namespace HH {
interface KeyedContainer implements HH\Container, HH\Rx\KeyedTraversable, \HH\Rx\KeyedTraversable {...}