ContainsKey

:::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. :::

Determines if the specified key is in the current ImmMap

public function containsKey(
  mixed $key,
): bool;

This function is interchangeable with contains().

Guide

• Constraints

Parameters

• mixed $key

Returns

• bool - true if the specified key is present in the current ImmMap; false otherwise.

Examples

See Map::containsKey for usage examples.