Change a nested value in an associative array given an array of keys that show the nested path

Question

I currently have an array in this format.

$test_arr = [
    'key1' => [
        'key2' => [
             'key3' => 'value',
         ],
    ],
    'key4' => 'value 2',
    'key5' => 'value 3',
];

My goal is to be able to replace 'value' in key3 with another value. The structure of the test_arr is not going to be known and will be completely different every single time, so I'm using a function to find the spot in the array where it is.

function array_find_deep($array, $search, $keys = array())
{
    foreach($array as $key => $value) {
        if (is_array($value)) {
            $sub = array_find_deep($value, $search, array_merge($keys, array($key)));
            if (count($sub)) {
                return $sub;
            }
        } elseif ($value === $search) {
            return array_merge($keys, array($key));
        }
    }

    return array();
}

When I use this function with my test array like so:

$key = array_find_deep($test_arr, 'value');

it returns an array with the contents:

['key1','key2','key3']

I now know the path in the array I need to go to, but I'm not sure how to take advantage of this to change the value of key3

I've made an attempt by creating another function

function replaceValueWithKeyMap($key, &$arr, $new_val, &$i = 0) {
    $length = count($key);
    if ($i >= $length-1) {
        $arr[$key[$i]] = $new_val;
        return $arr;
    } else {
        $i++;           
        replaceValueWithKeyMap($key, $arr[$key[$i]], $new_val, $i);
    }
}

but when I do

replaceValueWithKeyMap($key,$test_arr,'newvalue');

I just get back

$test_arr = [
    'key1' => [
        'key2' => [
             'key3' => 'value',
         ],
    ],
    'key4' => 'value 2',
    'key5' => 'value 3',
    'key3' => [
       'key3' => 'newvalue',
    ],
 ];

If I have an array of the path of keys how do I take advantage of that to change a value using that path.

Syscall · Accepted Answer · 2018-04-17 15:28:58Z

In your function replaceValueWithKeyMap(), you can avoid a recursive call, by looping over the keys and hold a reference of the current "path" in the array.

function replaceValueWithKeyMap($keys, &$arr, $new_val) {
    if (empty($keys)) return ; // Don't change $arr if $keys is empty
    $ref =& $arr ; // path starts with the root of $arr
    foreach ($keys as $key) { // for each keys
        $ref =& $ref[$key] ; // update the path
    }
    $ref = $new_val; // apply the new value
}

Will outputs:

Array
(
    [key1] => Array
        (
            [key2] => Array
                (
                    [key3] => newvalue
                )

        )

    [key4] => value 2
    [key5] => value 3
)

The complete code (demo) :

function array_find_deep($array, $search, $keys = array())
{
    foreach($array as $key => $value) {
        if (is_array($value)) {
            $sub = array_find_deep($value, $search, array_merge($keys, array($key)));
            if (count($sub)) {
                return $sub;
            }
        } elseif ($value === $search) {
            return array_merge($keys, array($key));
        }
    }

    return array();
}
function replaceValueWithKeyMap($keys, &$arr, $new_val) {
    if (empty($keys)) return ; // Don't change $arr if $keys is empty
    $ref =& $arr ; // path starts with the root of $arr
    foreach ($keys as $key) { // for each keys
        $ref =& $ref[$key] ; // update the path
    }
    $ref = $new_val; // apply the new value
}
$test_arr = [
    'key1' => [
        'key2' => [
             'key3' => 'value',
         ],
    ],
    'key4' => 'value 2',
    'key5' => 'value 3',
];

$key = array_find_deep($test_arr, 'value');
replaceValueWithKeyMap($key,$test_arr,'newvalue');
print_r($test_arr);

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