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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 `$array` , callable `$callback` [, mixed `$initial` = `NULL` ] )

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

### Parameters

`array`

  The input array.

`callback`
  mixed callback ( mixed `$carry` , mixed `$item` )
  `carry`

    Holds the return value of the previous iteration; in the case of the first iteration it instead holds the value of `initial`.

  `item`

    Holds the value of the current iteration.

`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 sum($carry, $item)
{
$carry += $item;
return $carry;
}
function multiplication($carry, $item)
{
$carry *= $item;
return $carry;
}
$a = array(1, 2, 3, 4, 5);
$x = array();
var_dump(array_reduce($a, "sum")); // int(15)
var_dump(array_reduce($a, "multiplication", 10)); // int(1200), because: 10*1*2*3*4*5
var_dump(array_reduce($x, "sum", "No data to reduce")); // string(17) "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