The HH\Traversable<Tv> interface

This page is a quick reference for people already familiar with the class. If this is new to you, we strongly recommend reading the introductory guides first:

Represents an entity that can be iterated over using foreach, without requiring a key.

The iteration variable will have a type of T.

In addition to Hack collections, PHP arrays and anything that implement Iterator are Traversable.

In general, if you are implementing your own Hack class, you will want to implement Iterable instead of Traversable since Traversable is more of a bridge for PHP arrays to work well with Hack collections.

Interface synopsis

interface Traversable {...}