Question

• I want a function that
  searches through my array, and
  returns all the
  children to a specific node. What is
  the most appropriate way to do this?
  Will recursion be necessary in this case?

I have previously constructed a few quite complex functions that iterates with or without the help of recursion through multi-dimensional arrays and re-arranging them, but this problem makes me completely stuck and I can’t just get my head around it…

Here’s my array:

Array
(
    [1] => Array (
            [id] => 1
            [parent] => 0

        )

    [2] => Array (
            [id] => 2
            [parent] => 1
        )

    [3] => Array (
            [id] => 3
            [parent] => 2
        )
)

UPDATE:

The output which I want to get. Sorry for the bad example, but I’ll blame it on lack of knowledge on how to format the stuff I need to do 🙂

function getAllChildren($id) {
    // Psuedocode
    return $array;
}

getAllChildren(1); // Outputs the following:

Array
(
    [2] => Array (
            [id] => 2
            [parent] => 1
        )

    [3] => Array (
            [id] => 3
            [parent] => 2
        )
)

Answer 1

$nodes = array( 1   => array (  'id'        => 1,
                                'parent'    => 0
                             ),
                2   => array ( 'id'         => 2,
                               'parent'     => 1
                             ),
                3   => array ( 'id'         => 3,
                               'parent'     => 2
                             )
                );


function searchItem($needle,$haystack) {
    $nodes = array();
    foreach ($haystack as $key => $item) {
        if ($item['parent'] == $needle) {
            $nodes[$key] = $item;
            $nodes = $nodes + searchItem($item['id'],$haystack);
        }
    }
    return $nodes;
}


$result = searchItem('1',$nodes);
echo '<pre>';
var_dump($result);
echo '</pre>';

Non-recursive version of the searchItem() function:

function searchItem($needle,$haystack) {
    $nodes = array();
    foreach ($haystack as $key => $item) {
        if (($item['parent'] == $needle) || array_key_exists($item['parent'],$nodes)) {
            $nodes[$key] = $item;
        }
    }
    return $nodes;
}

(assumes ordering of the parents/children, so a child node isn’t included in the array unless the parent is already there)