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
8.0.0 If callback expects a parameter to be passed by reference, this function will now emit an E_WARNING.

Examples

Example #1 array_reduce example

<?php
function sum($carry, $item)
{
    $carry += $item;
    return $carry;
}

function product($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, "product", 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
  • array_map
  • array_unique
  • array_count_values