DocumentationHackReferenceClassHH\MapmapWithKey

HH\Map::mapWithKey

Returns a Map after an operation has been applied to each key and value in the current Map

public function mapWithKey<Tu>(
  (function(Tk, Tv): Tu) $callback,
): Map<Tk, Tu>;

Every key and value in the current Map is affected by a call to mapWithKey(), unlike filterWithKey() where only values that meet a certain criteria are affected.

The keys will remain unchanged from the current Map to the returned Map. The keys are only used to help in the mapping operation.

Parameters

(function(Tk, Tv): Tu) $callback - The callback containing the operation to apply to the current Map keys and values.

Returns

Map<Tk, Tu> - a Map containing the values after a user-specified operation on the current Map's keys and values is applied.

Examples

This example shows how mapWithKey can be used to create a new Map based on $m's keys and values:

$m = Map {
  'red' => '#ff0000',
  'green' => '#00ff00',
  'blue' => '#0000ff',
  'yellow' => '#ffff00',
};

$css_colors = $m->mapWithKey(
  ($color, $hex_code) ==> "color: {$hex_code}; /* {$color} */",
);

echo implode("\n", $css_colors)."\n";

Output

color: #ff0000; /* red */
color: #00ff00; /* green */
color: #0000ff; /* blue */
color: #ffff00; /* yellow */