LastKey

:::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 the last key in the current Map

public function lastKey(): ?Tk;

Returns

• ?Tk - The last key in the current Map, or null if the Map is empty.

Examples

This example shows how lastKey() can be used even when a Map may be empty:

$m = Map {
  'red' => '#ff0000',
  'green' => '#00ff00',
  'blue' => '#0000ff',
  'yellow' => '#ffff00',
};
\var_dump($m->lastKey());

$m = Map {};
\var_dump($m->lastKey());