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# array_reduce

(PHP 4 >= 4.0.5)

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

## Description

mixed array_reduce ( array input, callback function [, int initial])

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

Example 1. array_reduce() example
    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", 1);

This will result in `$b` containing `15`, `$c` containing `1200` (= 1*2*3*4*5*10), and `$d` containing `1`.

See also array_filter() and array_map().

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