# reduceRight()

{% code title="Example.php" %}

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

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

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



$arrayUtils->reduceRight(
    function($accumulator, $value){
        echo  "$accumulator * $value = " . ($accumulator * $value) . PHP_EOL;
        return $accumulator * $value; }, 1));
//echo 1 * 10 = 10
//echo 10 * 9 = 90
//echo 90 * 8 = 720
//echo 720 * 7 = 5040
//echo 5040 * 6 = 30240
//echo 30240 * 5 = 151200
//echo 151200 * 4 = 604800
//echo 604800 * 3 = 1814400
//echo 1814400 * 2 = 3628800
//echo 3628800 * 1 = 3628800
//expected output: 3628800
```

{% endcode %}

## Syntax

```php
$arrayUtils->reduceRight(callable $callback, mixed $initialValue = null) : mixed;
```

### Parameter

* `$callback`

  > A function that produces an element of the new Array, taking four arguments:
  >
  > * `$accumulator`The accumulator accumulates callback's return values. It is the accumulated value previously returned in the last invocation of the callback—or `$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` <img src="https://2976351099-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MKYhyHaArG9Gsnmdxc8%2F-MKk9I82AGQBHkmwnVvk%2F-MKk9YjCz_YkVR1YiRy-%2FBADGE_OPTIONAL.svg?alt=media&#x26;token=3fbbac84-2f1b-40af-a991-b2eff659866a" alt="" data-size="line">&#x20;
  * A value to use as the first argument to the first call of the callback.

### Return value

* The result value.

## Prefixing

```php
ArrayUtils::reduceRightFrom(iterable $from, callable $callback, mixed $initialValue = null) : mixed;
```

## References

{% content-ref url="" %}
[](https://arrayutils.docs.present.kim/methods/g/reduce)
{% endcontent-ref %}

{% embed url="<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/ReduceRight>" %}