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filterWithKey

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 MutableSet containing the values of the current MutableSet that meet a supplied condition applied to its "keys" and values

public function filterWithKey(
  (function(arraykey, Tv): bool) $fn,
): MutableSet<Tv>;

Since sets don't have keys, the callback uses the values as the keys as well.

Only values that meet a certain criteria are affected by a call to filterWithKey(), while all values are affected by a call to mapWithKey().

Parameters​

  • (function(arraykey, Tv): bool) $fn - The callback containing the condition to apply to the current MutableSet "keys" and values.

Returns​