Manipulating the structure of a multidimensional array

Question

This is actually a problem that I've already solved, but I suspect that there may be a better solution. I have a nested array which basically represents a list of all the nodes from a category tree (in no particular order):

Array(
    [0] => Array(
        [Category] => Array(
            [id] => 49
            [name] => Poster
        )
        [Child] => Array()
    )
    [1] => Array(
        [Category] => Array(
            [id] => 48
            [name] => Sticker
        )
        [Child] => Array()
    )
    [2] => Array(
        [Category] => Array(
            [id] => 46
            [name] => Hat
        )
        [Child] => Array()
    )
    [3] => Array(
        [Category] => Array(
            [id] => 45
            [name] => Hoodie
        )
        [Child] => Array()
    )
)

You'll notice that $node['Child'] is an empty array in all instances. This is because I've already used array_filter() to filter out all non-leaf-nodes. Still, what I ultimately want is to have a single-dimensional array of the leaf nodes like this:

Array(
    [49] => Poster
    [48] => Sticker
    [46] => Hat
    [45] => Hoodie
)

So what would be the most elegant way of converting the first array to the second array?

Optionally, you can also start with an array of both leaf-nodes and non-leaf-nodes, and try to both prune the array and restructure it. An example of a non-leaf-node would be something like:

[7] => Array(
    [Category] => Array(
        [id] => 36
        [name] => Merch
    )
    [Child] => Array(
        [0] => Array(
            [id] => 49
            [name] => Poster
        )
        [1] => Array(
            [id] => 48
            [name] => Sticker
        )
        [2] => Array(
            [id] => 40
            [name] => Apparel
        )
    )
)

Lastly, I'm using CakePHP, so use of CakePHP's Set class is also acceptable.

Answer 1

Elegant? Define elegant. I think some people are going to turn this into a golf contest as opposed to simply doing what makes sense and is evident to anyone stumbling upon the code later on:

$cats = array();
foreach($categories as $c) {
    $cats[$c['Category']['id']] = $c['Category']['name'];
}

I suspect this is what you have, in which case I suggest you pat yourself in the back and move on.

Answer 2

This answer is not in anyway intended to be "elegant", but I suppose it might fall under the "clever" category. (Note: clever solutions are not always "good" solutions)

preg_match_all( "/\"name\";s:\d+:\"(.*?)\"/i", serialize( $arr ), $matches );

print_r( $matches[1] );

In all honesty, recursive iteration is the best choice for clarity, even if it's not terribly efficient or concise.

$arr = array(
    "0" => array(
        "Category" => array(
            "id" => 49
            ,"name" => Poster
        )
        ,"Child" => array()
    )
    ,"1" => array(
        "Category" => array(
            "id" => 48
            ,"name" => Sticker
        )
        ,"Child" => array()
    )
    ,"2" => array(
        "Category" => array(
            "id" => 46
            ,"name" => Hat
        )
        ,"Child" => array()
    )
    ,"3" => array(
        "Category" => array(
            "id" => 45
            ,"name" => Hoodie
        )
        ,"Child" => array(
            "0" => array(
                "id" => 49
                ,"name" => Poster
            )
            ,"1" => array(
                "id" => 48
                ,"name" => Sticker
            )
            ,"2" => array(
                "id" => 40
                ,"name" => Apparel
            )
        )
    )
);

findNames( $arr, $names );
echo '<pre>';
print_r( $names );
echo '</pre>';

function findNames( $source, &$out )
{
    foreach ( $source as $value )
    {
     if ( isset( $value['name'] ) )
     {
      // Assumes that if $value['name'] exists, $value['id'] must also exist
      $out[$value['id']] = $value['name'];
      continue;
     }
     if ( is_array( $value ) )
     {
      findNames( $value, &$out );
     }
    }
}