KeyedContainer

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

KeyedContainer allows you to do (foreach $value as $k => $v, $value[$key]) and is an interface used by both Hack arrays (vec/dict/keyset) and Hack collections (Vector/Map/Set)

If you need to iterate over an array / collection with keys, use KeyedContainer; otherwise, use Container. Without iterating, you can access keys directly: $keyed_container[$key].

Guides

• Introduction
• Interfaces
• Read Write

Interface Synopsis

namespace HH;

interface KeyedContainer implements Container<Tv>, KeyedTraversable<Tk, Tv> {...}