Use an array as an index to access a multidimensional array in PHP

Question

I am having a problem accessing an object in a multidimensional array.

THE CONTEXT

Basically, I have an object (category) which consists of Name, ID, ParentID and more. I also have an array ultimateArray which is multidimentional.

For a given category, I am writing a function (getPath()) that will return an array of ids. For example, an object named Granny Smith has a parentID of 406 and is therefore a child of Food(5) -> Fruits(101) -> Apples(406). The function will return either an array or string of the ids of the objects parents. In the above example this would be: 5 -> 101 -> 406 or ["5"]["101"]["406"] or [5][101][406]. Food is a root category!

THE PROBLEM

What I need to do is use whatever is returned from getPath() to access the category id 406 (Apples) so that I can add the object Granny Smith to the children of Apples.

The function $path = $this->getPath('406'); is adaptable. I am just having difficulty using what is returned in the following line:

$this->ultimate[$path]['Children'][]= $category;

It works when I hard code in:

$this->ultimate["5"]["101"]["406"]['Children'][]= $category;
//or
$this->ultimate[5][101][406]['Children'][]= $category;

Any help is much appreciated.

getPath() can return anything. At the moment I return an array ["5"]["101"]["406"] but can easily change the code to return a string of indexes or anything else. — Patrick
– Patrick, Commented May 3, 2013 at 14:41
["5"]["101"]["406"] isn't an array at all! So, are you returning the element inside that slice of array? Or a string that contains what you had wrote? What ? :) — DonCallisto
– DonCallisto, Commented May 3, 2013 at 14:44
it might help if you posted the code where you create $ultimate so we can see how your array is structured and the relation ship between the different levels. is it an associative array, such that "food" => 5, "fruits" => 101, "apples" => 406, or is it a tiered array of arrays, such that "food" => array ("fruits", "vegetables", etc) — Jeff Hawthorne
– Jeff Hawthorne, Commented May 3, 2013 at 14:50
The getPath() function is not the issue I am having - it simply creates an array or list of the indexes to access the relevant category. What I am struggling with is how to use these indexes to access the parent category of Granny Smith. Please see updated question which details what works when hard coded in. — Patrick
– Patrick, Commented May 3, 2013 at 14:52

Willy Pt · Accepted Answer · 2013-05-03 15:18:45Z

2

Suppose you have the array like below

<?php
$a = array(
        12 => array(
                65 => array(
                    90 => array(
                        'Children' => array()
                    )
                )
            )
    );

$param = array(12, 65, 90); // your function should return values like this
$x =& $a; //we referencing / aliasing variable a to x
foreach($param as $p){
    $x =& $x[$p]; //we step by step going into it
}
$x['Children'] = 'asdasdasdasdas';
print_r($a);

?>`

You can try referencing or aliasing it
http://www.php.net/manual/en/language.references.whatdo.php
The idea is to make a variable which is an alias of your array and going deep from the variable since we can't directly assigning multidimensional key from string (AFAIK)

output

Array
(
    [12] => Array
        (
            [65] => Array
                (
                    [90] => Array
                        (
                            [Children] => asdasdasdasdas
                        )

                )

        )

)

edited May 3, 2013 at 15:18

answered May 3, 2013 at 14:56

Willy Pt

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1 Comment

Patrick Over a year ago

It took a little bit of adapting, but I think your code has worked brilliantly (and now I understand referencing better)! Thanks so much! I will comment my changes and mark as correct when its all tidy and I have a working solution.

nvanesch · Accepted Answer · 2013-05-03 14:50:30Z

You can use a recursive function to access the members. This returns NULL if the keys do not correspond with the path, but you could also throw errors or exceptions there. Also please note that i have added "Children" to the path. I have done this so you can use this generically. I just did an edit to show you how to do it without children in the path.

<?php

$array = array(1 => array(2 => array(3 => array("Children" => array("this", "are", "my", "children")))));
$path = array(1, 2, 3, "Children");
$pathWithoutChildren = array(1, 2, 3);

function getMultiArrayValueByPath($array, $path) {
    $key = array_shift($path);
    if (array_key_exists($key, $array) == false) {
        // requested key does not exist, in this example, just return null
        return null;
    }
    if (count($path) > 0) {
        return getMultiArrayValueByPath($array[$key], $path);
    }
    else {
        return $array[$key];
    }
}

var_dump(getMultiArrayValueByPath($array, $path));
$results = getMultiArrayValueByPath($array, $pathWithoutChildren);
var_dump($results['Children']);

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