PHP reference

array_walk

Calls a function for every element of an array.

Syntax

array_walk(array|object &$array, callable $callback, mixed $arg = null): true

Parameter	Type	Description
$array	array\|object	The array.
$callback	callable	A function that receives the value and the key.
$arg	mixed	Optional. An extra argument for the function.

trueAlways `true`.

The value and the key in the function:

<?php
 
$prices = ['tea' => 250, 'coffee' => 400];
 
array_walk($prices, function ($price, $name) {
    echo $name, ': ', $price, "\n";
});

Output:

tea: 250
coffee: 400

Changing elements by reference:

<?php
 
$prices = ['tea' => 250, 'coffee' => 400];
 
array_walk($prices, function (&$price) {
    $price *= 2;
});
 
echo json_encode($prices);

Output:

{"tea":500,"coffee":800}

Unlike array_map(), the function builds no new array and passes the key to the handler. A plain foreach loop does the same and reads more easily.

Array functions — Processing arrays in PHP without loops — array_map, array_filter, array_reduce, searching and slicing.