Find parent key of match in a multidimensional array

Question

I'm trying to find a way to return the value of an array's parent key.

For example, from the array below I'd like to find out the parent's key where $array['id'] == "0002". The parent key is obvious because it's defined here (it would be 'products'), but normally it'd be dynamic, hence the problem. The 'id' and value of 'id' is known though.

    [0] => Array
        (
            [data] => 
            [id] => 0000
            [name] => Swirl
            [categories] => Array
                (
                    [0] => Array
                        (
                            [id] => 0001
                            [name] => Whirl
                            [products] => Array 
                               (
                                    [0] => Array
                                        (
                                            [id] => 0002
                                            [filename] => 1.jpg
                                         )
                                    [1] => Array
                                        (
                                            [id] => 0003
                                            [filename] => 2.jpg
                                         )
                                )
                         )
                 )
          )

deceze · Accepted Answer · 2010-03-24 02:39:03Z

3

A little crude recursion, but it should work:

function find_parent($array, $needle, $parent = null) {
    foreach ($array as $key => $value) {
        if (is_array($value)) {
            $pass = $parent;
            if (is_string($key)) {
                $pass = $key;
            }
            $found = find_parent($value, $needle, $pass);
            if ($found !== false) {
                return $found;
            }
        } else if ($key === 'id' && $value === $needle) {
            return $parent;
        }
    }

    return false;
}

$parentkey = find_parent($array, '0002');

edited Mar 24, 2010 at 2:39

answered Mar 24, 2010 at 1:23

deceze♦

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4 Comments

alex Over a year ago

I'm not too familiar with recursion, but I coded up a similar answer to this, only I used a 'static' variable to replace the $parent argument you use. Is either way better?

deceze Over a year ago

@alex static would probably work fine as well. I have to admit I'm not much of a static user. :) It'd eliminate the need to pass along the extra variable. OTOH, in the above function you can specify a "default" parent... Either one's okay I guess. :)

alex Over a year ago

Thanks, I understand the benefits of your method. +1

jmbertucci Over a year ago

I'm curious, is there a better data structure to use instead of an array if one has this need? It's been a long time since I had some good programming training but would a Linked List work better? That way you don't have to search through an array every time you want a given parent (think of returning every parent of a child until the root). Though, I've yet to really use linked lists in PHP. Perhaps they're not that easy to do?

Ignacio Vazquez-Abrams · Accepted Answer · 2010-03-24 01:17:49Z

2

Since you have a tree structure either of a BFS or DFS can do it. Since the structure is variable a recursive solution would work well. Simply return a sentinel when you find the value, then return the key in the caller.

answered Mar 24, 2010 at 1:17

Ignacio Vazquez-Abrams

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Comments

Ajean · Accepted Answer · 2017-05-18 01:07:42Z

-3

function array_to_xml($array, $rootElement = null, $xml = null) {

    $_xml = $xml;

    if ($_xml === null) {
        $_xml = new SimpleXMLElement($rootElement !== null ? $rootElement : '<root/>');
    }

    $has_int_key = 0;

    foreach ($array as $k => $v) {
        if (is_array($v)) {
            if(is_int($k)){
                $this->array_to_xml($v, $k, $_xml->addChild($rootElement));
            } 
            else {
                foreach($v as $key=>$value) {
                    if(is_int($key)) $has_int_key = 1;
                }

              if ($has_int_key) {
                  $this->array_to_xml($v, $k, $_xml);
              } else {
                  $this->array_to_xml($v, $k, $_xml->addChild($k));
              }
            }
        } 
        else {
            $_xml->addChild($k, $v);
        }
    }

    return $_xml->asXML();

}

edited May 18, 2017 at 1:07

Ajean

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answered May 17, 2017 at 19:07

chla

1

1 Comment

Ali Qorbani Over a year ago

you have posted a code snipped without any description or comment. also as your code shows it works with xml data. its not related with the question!

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