Convert delimited string into array key path and assign value

Question

I have a string like this:

$string = 'one/two/three/four';

which I turn it into a array:

$keys = explode('/', $string);

This array can have any number of elements, like 1, 2, 5 etc.

How can I assign a certain value to a multidimensional array, but use the $keys I created above to identify the position where to insert?

Like:

$arr['one']['two']['three']['four'] = 'value';

Sorry if the question is confusing, but I don't know how to explain it better

[Using a string path to set nested array data](https://stackoverflow.com/q/9628176/2943403) , [Is there something like keypath in an associative array in PHP?](https://stackoverflow.com/q/16389168/2943403) , [Convert a string into an associative array key?](https://stackoverflow.com/q/34009699/2943403) , [String to multidimensional array path](https://stackoverflow.com/q/21379382/2943403) , [Array path from variable in PHP](https://stackoverflow.com/q/5820879/2943403) — mickmackusa, Feb 17 '23 at 23:15

score 15 · Accepted Answer · answered Sep 22 '11 at 01:07

This is kind of non-trivial because you want to nest, but it should go something like:

function insert_using_keys($arr, $keys, $value){
    // we're modifying a copy of $arr, but here
    // we obtain a reference to it. we move the
    // reference in order to set the values.
    $a = &$arr;

    while( count($keys) > 0 ){
        // get next first key
        $k = array_shift($keys);

        // if $a isn't an array already, make it one
        if(!is_array($a)){
            $a = array();
        }

        // move the reference deeper
        $a = &$a[$k];
    }
    $a = $value;

    // return a copy of $arr with the value set
    return $arr;
}

score 9 · Answer 2 · answered Sep 22 '11 at 01:09

9

$string = 'one/two/three/four';
$keys = explode('/', $string);
$arr = array(); // some big array with lots of dimensions
$ref = &$arr;

while ($key = array_shift($keys)) {
    $ref = &$ref[$key];
}

$ref = 'value';

What this is doing:

Using a variable, $ref, to keep track of a reference to the current dimension of $arr.
Looping through $keys one at a time, referencing the $key element of the current reference.
Setting the value to the final reference.

answered Sep 22 '11 at 01:09

FtDRbwLXw6

27,774
13
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I get a "connection closed by server" when I try this :) – Alex Sep 22 '11 at 01:14
What if `$keys` contains 0 or NULL? – Mark Elliot Sep 22 '11 at 01:16
He asked how to solve the problem, not write error-checking for it :) – FtDRbwLXw6 Sep 22 '11 at 01:17
It's possible to solve the problem even given those conditions, your code fails miserably in that situation. – Mark Elliot Sep 22 '11 at 01:30
2

And your solution "fails miserably" when `$arr` is not an array, along with a handful of other cases. Bullet-proof error-checking is not a prerequisite for a correct answer. – FtDRbwLXw6 Sep 22 '11 at 01:34
for anyone needing the same: I modified this wonderful piece of code to `$ref = &$ref['children'][$key]`because I need all children together in one array sub node. – jasie Jan 17 '20 at 10:23

score 1 · Answer 3 · answered Sep 22 '11 at 01:07

You'll need to first make sure the key's exist, then assign the value. Something like this should work (untested):

function addValueByNestedKey(&$array, $keys, $value) {
    $branch = &$array;
    $key = array_shift($keys);
    // add keys, maintaining reference to latest branch:
    while(count($keys)) {
        $key = array_pop($keys);
        if(!array_key_exists($key, $branch) {
            $branch[$key] = array();
        }
        $branch = &$branch[$key];
    }
    $branch[$key] = $value;
}

// usage:
$arr = array();
$keys = explode('/', 'one/two/three/four');

addValueByNestedKey($arr, $keys, 'value');

MattoTodd · Answer 4 · 2011-09-22T01:32:01.480

1

it's corny but:

function setValueByArrayKeys($array_keys, &$multi, $value) {
     $m = &$multi
     foreach ($array_keys as $k){
         $m = &$m[$k];
     }
     $m = $value;
}

edited Sep 22 '11 at 01:32

answered Sep 22 '11 at 01:07

MattoTodd

14,467
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This won't work. `$multi = $multi[$k]` creates a *copy*, it's not a reference, so you're not actually modifying anything when you do `$multi = $value`, except the final array. – Mark Elliot Sep 22 '11 at 01:11
it *still* won't work, you're creating *copies*, not *references*. – Mark Elliot Sep 22 '11 at 01:15
sorry bro, i'm a python guy and by default you get references in python, edited AGAIN – MattoTodd Sep 22 '11 at 01:15
So believe it or not, this still doesn't do what you expect, taking `$multi` as a parameter generates a copy, the first reference you assign to `$m` is to the *copy*, not the *original*. You can (a) make `$multi` a reference in the parameter list or (b) `return $multi`. – Mark Elliot Sep 22 '11 at 01:29
1

In general, if you're not familiar with the target language, you ought to run your code. – Mark Elliot Sep 22 '11 at 01:29

score 0 · Answer 5 · answered Apr 22 '19 at 11:58

    $arr['one']['two']['three']['four'] = 'value';

    $string = 'one/two/three/four';
    $ExpCheck = explode("/", $string);
    $CheckVal = $arr;
    foreach($ExpCheck AS $eVal){
        $CheckVal = $CheckVal[$eVal]??false;
        if (!$CheckVal)
            break;
    }
    if ($CheckVal) {
        $val =$CheckVal;
    }

this will give u your value in array.

Convert delimited string into array key path and assign value

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