DifferenceByKey

:::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. :::

Returns a new ImmMap with the keys that are in the current ImmMap, but not in the provided KeyedTraversable

public function differenceByKey(
  KeyedTraversable<mixed, mixed> $traversable,
): ImmMap<Tk, Tv>;

Parameters

• KeyedTraversable<mixed,mixed> $traversable - The KeyedTraversable on which to compare the keys.

Returns

• ImmMap<Tk,Tv> - An ImmMap containing the keys (and associated values) of the current ImmMap that are not in the KeyedTraversable.

Examples

See Map::differenceByKey for usage examples.