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mapWithKey

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 ImmVector containing the results of applying an operation to each key/value pair in the current ImmVector

public function mapWithKey<Tu>(
  (function(int, Tv): Tu) $callback,
): ImmVector<Tu>;

mapWithKey()'s result contains a value for every key/value pair in the current ImmVector; unlike filterWithKey(), where only values whose key/value pairs meet a certain criterion are included in the resulting ImmVector.

Parameters​

  • (function(int, Tv): Tu) $callback

Returns​

Examples​

See Vector::mapWithKey for usage examples.