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slice

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 ConstMap 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,
): ConstMap<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 ConstMap will always be a proper subset of the current ConstMap.

Parameters​

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

Returns​

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