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