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takeWhile

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 an ImmMap containing the keys and values of the current ImmMap up to but not including the first value that produces false when passed to the specified callback

public function takeWhile(
  (function(Tv): bool) $callback,
): ImmMap<Tk, Tv>;

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

Parameters​

  • (function(Tv): bool) $callback

Returns​

  • ImmMap<Tk,Tv> - An ImmMap that is a proper subset of the current ImmMap up until when the callback returns false.

Examples​

See Map::takeWhile for usage examples.