TakeWhile

:::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 KeyedIterable containing the values of the current KeyedIterable up to but not including the first value that produces false when passed to the specified callback

public function takeWhile(
  (function(Tv): bool) $fn,
): KeyedIterable<Tk, Tv>;

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

Parameters

• (function(Tv): bool) $fn - The callback that is used to determine the stopping condition.

Returns

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