Slice

:::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 subset of the current Map starting from a given key location up to, but not including, the element at the provided length from the starting key location

public function slice(
  int $start,
  int $len,
): Map<Tk, Tv>;

$start is 0-based. $len is 1-based. So slice(0,2) would return the keys and values at key location 0 and 1.

The returned Map will always be a proper subset of the current Map.

Parameters

• int $start - The starting key location of the current Map for the returned Map.
• int $len - The length of the returned Map.

Returns

• Map<Tk,Tv> - A Map that is a proper subset of the current Map starting at $start up to but not including the element $start + $len.

Examples

$m = Map {
  'red' => '#ff0000',
  'green' => '#00ff00',
  'blue' => '#0000ff',
  'yellow' => '#ffff00',
  'purple' => '#663399',
};

// Start at key index 1 ('green') and include 3 elements
$m2 = $m->slice(1, 3);

\var_dump($m2);