Passing user data as reference to array_walk_recursive in Php

Question

I try to pass a third parameter via reference to Phps array_walk_recursive

$field = 'foo';

array_walk_recursive($config, function($value, $key, &$field) {

    $field = 'bar';

}, $field);

echo $field // 'foo'

Why is $field still 'foo', though it has been passed to the function as reference?

Answer 1

According to the php documentation of anonymous functions inherited variables of a closure have to be defined in the functions header with the keyword use which leaves my example with:

function($value, $key) use (&$field) { ... }

Though the callback function inherits the parameters declared with use from its parent which means from the scope/function it has been declared (not executed) in.

Answer 2

 <?php
        $field = array('foo');
        array_walk_recursive($field, function($value, $key) use(&$field) {
            $field = 'bar';
        });
        print_r($field);
        ?>