At

:::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 value at the specified key in the current Map

public function at(
  Tk $key,
): Tv;

If the key is not present, an exception is thrown. If you don't want an exception to be thrown, use get() instead.

$v = $map->at($k) is equivalent to $v = $map[$k].

Parameters

• Tk $key

Returns

• Tv - The value at the specified key; or an exception if the key does not exist.

Examples

This example prints the values at the keys red and green in the Map:

$m = Map {
  'red' => '#ff0000',
  'green' => '#00ff00',
  'blue' => '#0000ff',
  'yellow' => '#ffff00',
};

// Print the value at the key 'red'
\var_dump($m->at('red'));

// Print the value at the key 'yellow'
\var_dump($m->at('yellow'));

This example throws an OutOfBoundsException because the Map has no key 'blurple':

$m = Map {
  'red' => '#ff0000',
  'green' => '#00ff00',
  'blue' => '#0000ff',
  'yellow' => '#ffff00',
};

// Key 'blurple' doesn't exist (this will throw an exception)
\var_dump($m->at('blurple'));