array_walk()

array_walk() — Apply a user supplied function to every member of an array.

Built-in function of PHP 8.5. The manual lists it as available in PHP 4, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.

What it does

array_walk() is not affected by the internal array pointer of array. array_walk() will walk through the entire array regardless of pointer position.

Signature

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

Parameters

Parameter	Type	What it takes
&$array	array\|object	The input array.
$callback	callable	Typically, callback takes on two parameters. The array parameter's value being the first, and the key/index second.
$arg	mixed	If the optional arg parameter is supplied, it will be passed as the third parameter to the callback.

Return value

Always returns true.

Example

A runnable snippet:

$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple"); function test_alter(&$item1, $key, $prefix) { $item1 = "$prefix: $item1"; } function test_print($item2, $key) { echo "$key. $item2\n"; } echo "Before ...:\n"; array_walk($fruits, 'test_print'); array_walk($fruits, 'test_alter', 'fruit'); echo "... and after:\n"; array_walk($fruits, 'test_print');

Output:

Before ...: d. lemon a. orange b. banana c. apple ... and after: d. fruit: lemon a. fruit: orange b. fruit: banana c. fruit: apple

Changelog

Version	Change
8.2.0	The return type is true now; previously, it was bool.
8.0.0	If callback expects the second or third parameter to be passed by reference, this function will now emit an E_WARNING.