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 Pair starting from a given key up to, but not including, the element at the provided length from the starting key

public function slice(
  int $start,
  int $len,
): ImmVector<mixed>;

$start is 0-based. $len is 1-based. So slice(0,2) would return the elements at key 0 and 1 (all of the current Pair elements).

Parameters

• int $start - The starting key of the current Pair to begin the returned ImmVector.
• int $len - The length of the returned ImmVector.

Returns

• ImmVector<mixed> - An ImmVector with values from the current Pair starting at $start up to but not including the element $start + $len.

Examples

$p = Pair {'foo', -1.5};

// Get an ImmVector of both values
\var_dump($p->slice(0, 2));

// Get an ImmVector of the first value
\var_dump($p->slice(0, 1));

// Get an ImmVector of the second value
\var_dump($p->slice(1, 1));