PHP Manual
Array Functions
Apply a user function recursively to every member of an array

array_walk_recursive

(PHP 5, PHP 7, PHP 8)

array_walk_recursive — Apply a user function recursively to every member of an array

Description

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

Applies the user-defined callback function to each element of the array. This function will recurse into deeper arrays.

Parameters

array: The input array.
callback: Typically, callback takes on two parameters. The array parameter's value being the first, and the key/index second.
Note:
If callback needs to be working with the actual values of the array, specify the first parameter of callback as a reference. Then, any changes made to those elements will be made in the original array itself.
arg: If the optional arg parameter is supplied, it will be passed as the third parameter to the callback.

Return Values

Always returns true.

Changelog

Version	Description
8.2.0	The return type is `true` now; previously, it was bool.

Examples

Example #1 array_walk_recursive() example

<?php
$sweet = array('a' => 'apple', 'b' => 'banana');
$fruits = array('sweet' => $sweet, 'sour' => 'lemon');

function test_print($item, $key)
{
echo "$key holds $item\n";
}

array_walk_recursive($fruits, 'test_print');
?>

The above example will output:

a holds apple
b holds banana
sour holds lemon

You may notice that the key 'sweet' is never displayed. Any key that holds an array will not be passed to the function.