Organize multidimensional array using Recursion

Question

I have an array that I've build dynamically. It has many nested arrays because of the way it's built, but the depth is useless to me, so I organize it right afterwards. It could look like this:

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [0] => Array
                        (
                            [0] => Array
                                (
                                    [index] => -1
                                    [cost] => 0.189956571618
                                )
                        )         
                )
        )

    [1] => Array
        (
            [index] => -1
            [cost] => 2.18650011647
        )
)

I want to almost-flatten this array (i.e. access its data using $array[$i]['cost'] on all entries, regardless if they were nested deep before I processed them). So far I've been using SPL recursion, with something along these lines:

function flatten($array) {
    $return = array();
    $it = new RecursiveIteratorIterator(new ParentIterator(new RecursiveArrayIterator($array)), RecursiveIteratorIterator::SELF_FIRST);
    foreach($it as $value) {
        if(isset($value['cost'])) {
            $return[] = $value;
        }
    }
    return $return;
}

It works for the most part, but some of the values in the original array, which do have a 'cost' index in them, fail to be added to the new array because they are passed as nested arrays themselves, like so:

Array
(
    [0] => Array
        (
            [index] => -1
            [cost] => 0.189956571618
        )

    [1] => Array
        (
            [index] => -1
            [cost] => 2.18650011647
        )
)

...instead of just (which most of the time I get):

Array
        (
            [index] => -1
            [cost] => 0.189956571618
        )

I thought the whole point of using a RecursiveIterator was to go deep within the array and fetch the entries which don't have arrays within them (i.e. the 'values' I want). Am I using the wrong tools for this job? If so, what would be more appropriate to loop through an array for which I don't know the depth? If SPL is the way to go, what am I doing wrong?

Thanks in advance.

You can't have two keys of the same name, so if you have a bunch of nested values under the key 'cost', you'll lose all but one. Rather, what is your data structure and what result do you want? — erisco
– erisco, Commented Aug 19, 2012 at 21:12
I've added more info to the question, including an example of what the array might look like before flattening. — Tomas Buteler
– Tomas Buteler, Commented Aug 19, 2012 at 21:22
@erisco: the final array would still have numerical keys, so I'm not overwriting each entry (see: $return[] = $value). I only want to remove the unlimited depth, and turn it into a simple, bi-dimensional array, regardless of how it looked before. — Tomas Buteler
– Tomas Buteler, Commented Aug 19, 2012 at 21:27

Valerij · Accepted Answer · 2012-08-19 23:12:40Z

1

you could use array_walk_recursive

EDIT

function flatten($array) {
    $return = array();
    array_walk_recursive($array, function($value, $key) use (&$return) {
        if(isset($value['cost']) $return[] = $value;
    });
    return $return;
}

on the SPL part EDIT long discussion in the chatroom, check OP's answer

edited Aug 19, 2012 at 23:12

answered Aug 19, 2012 at 21:17

Valerij

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6 Comments

Tomas Buteler Over a year ago

I've tried it once before, but couldn't get it to do what I wanted for some reason. Anyway, I'd like to stick to the RecursiveIterators, if possible, and make it return what I expected it to return, or at least learn why it's not.

Tomas Buteler Over a year ago

I've changed the order of the iterator, but I get an error: "Catchable fatal error: Argument 1 passed to ParentIterator::__construct() must implement interface RecursiveIterator, instance of RecursiveIteratorIterator given..."

Valerij Over a year ago

@tbuteler oh yeah, forgot to move the argument

Tomas Buteler Over a year ago

Hmmm... still get the same error, even after changing the argument's position.

Valerij Over a year ago

@tbuteler omit the RecursiveIteratorIterator part (notice for future me, answer qs on a machine you could test the answer before posting)

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