Iteratively reduce the array to a single value using a callback function

array_rand
array_replace_recursive
Array Functions
PHP Manual

# array_reduce

(PHP 4 >= 4.0.5, PHP 5)

array_reduce — Iteratively reduce the array to a single value using a callback function

### Description

mixed array_reduce ( array `$input` , callback `$function` [, mixed `$initial` = `NULL` ] )

array_reduce() applies iteratively the `function` function to the elements of the array `input`, so as to reduce the array to a single value.

### Parameters

`input`

  The input array.

`function`

  The callback function.

`initial`

  If the optional `initial` is available, it will be used at the beginning of the process, or as a final result in case the array is empty.

### Return Values

Returns the resulting value.

If the array is empty and `initial` is not passed, array_reduce() returns `NULL`.

### Changelog

Version | Description
--- | ---
5.3.0 | Changed `initial` to allow mixed , previously integer .

### Examples

Example #1 array_reduce() example

`<?php
function rsum($v, $w)
{
$v += $w;
return $v;
}
function rmul($v, $w)
{
$v *= $w;
return $v;
}
$a = array(1, 2, 3, 4, 5);
$x = array();
$b = array_reduce($a, "rsum");
$c = array_reduce($a, "rmul", 10);
$d = array_reduce($x, "rsum", "No data to reduce");
?>`

This will result in $b containing 15, $c containing 1200 (= 10*1*2*3*4*5), and $d containing No data to reduce.

### See Also

- array_filter() - Filters elements of an array using a callback function
- array_map() - Applies the callback to the elements of the given arrays
- array_unique() - Removes duplicate values from an array
- array_count_values() - Counts all the values of an array

array_rand
array_replace_recursive
Array Functions
PHP Manual