PHP | Ds\Map reduce() Function

The Ds\Map::reduce() function is an inbuilt function in PHP which is used to reduce the map to a single value by applying operations using the callback function.

Syntax:

mixed public Ds\Map::reduce( $callback, $initial )

Parameter: This function accepts two parameters as mentioned above and described below:

• $callback: This parameter holds the function which contains the operation on the elements and store carry. This callback function contains three arguments which are listed below:
  • carry: It holds the return value of the previous callback, or initial if it’s the first iteration.
  • key: It holds the key of the current iteration.
  • value: It holds the value of the current iteration.
• $initial: This parameter holds the initial value of carry, which can be NULL.

Return value: This function returns the final value returned by the callback function.

Below programs illustrate the Ds\Map::reduce() function in PHP:

Program 1:

Map Elements
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => a
            [value] => 1
        )

    [1] => Ds\Pair Object
        (
            [key] => b
            [value] => 3
        )

    [2] => Ds\Pair Object
        (
            [key] => c
            [value] => 5
        )

)

Element after performing operation
int(15)

Program 2:

Original map elements
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => a
            [value] => 10
        )

    [1] => Ds\Pair Object
        (
            [key] => b
            [value] => 20
        )

    [2] => Ds\Pair Object
        (
            [key] => c
            [value] => 30
        )

    [3] => Ds\Pair Object
        (
            [key] => d
            [value] => 40
        )

    [4] => Ds\Pair Object
        (
            [key] => e
            [value] => 50
        )

)

Map after reducing to single element
int(120000000)

Reference: https://www.php.net/manual/en/ds-map.reduce.php