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

public function filterWithKey(
  (function(arraykey, Tv): bool) $fn,
): ConstSet<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().


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