reduce()

The reduce() method iteratively reduce the array to a single value using a callback function

Example.php

<?php use kim\present\utils\arrays\ArrayUtils;

$arrayUtils = ArrayUtils::from(range(1, 10));

//This is like a 10 factorial
$arrayUtils->reduce(function($accumulator, $value){ return $accumulator * $value; }, 1);
// expected output: 3628800



$arrayUtils->reduce(
    function($accumulator, $value){
        echo  "$accumulator * $value = " . ($accumulator * $value) . PHP_EOL;
        return $accumulator * $value; }, 1));
//echo 1 * 1 = 1
//echo 1 * 2 = 2
//echo 2 * 3 = 6
//echo 6 * 4 = 24
//echo 24 * 5 = 120
//echo 120 * 6 = 720
//echo 720 * 7 = 5040
//echo 5040 * 8 = 40320
//echo 40320 * 9 = 362880
//echo 362880 * 10 = 3628800
//expected output: 3628800

Syntax

$arrayUtils->reduce(callable $callback, mixed $initialValue = null) : mixed;

Parameter

• $callback

  A function that produces an element of the new Array, taking four arguments:

  • $accumulatorThe accumulator accumulates callback's return values. It is the accumulated value previously returned in the last invocation of the callback—or $initialValue, if it was supplied (see below).

  • $value The current element being processed in the array.

  • $key The index of the current element being processed in the array.

  • $array The array every was called upon.

• $initialValue

  • A value to use as the first argument to the first call of the callback.

Return value

• The result value.

Prefixing

ArrayUtils::reduceFrom(iterable $from, callable $callback, mixed $initialValue = null) : mixed;

References

PHP: array_reduce - Manual

Array.prototype.reduce() - JavaScript | MDN