Question

Given an array:

0 => (
    [parent_id] => null,
    [name] => "Root"
    [children] => array(
        10 => array(
            [parent_id] => 0,
            [name] => "Category A",
            [children] => array(
                30 => array(
                    [parent_id] => 10,
                    [name] => "Category C"
                )
            )
        ),
        20 => array(
            [parent_id] => 0,
            [name] => "Category B"
        )
    )
)

I need to return an array of string representations of those paths…

array(
    [0] => "Root",
    [10] => "Root > Category A",
    [30] => "Root > Category A > Category C",
    [20] => "Root > Category B"
)

I’ve been messing around doing this recursively but I’m having some trouble doing it efficiently. Are there simple ways to do this that I’m just overlooking?

EDIT:

Solution is simply a slightly modified version of Alexander Varwijk’s answer. A few tweaks to handle non-existent children, calling the function recursively via FUNCTION constant so it’s easy to change the function name and a change from array_merge to the + operator to combine the arrays in order to preserve keys.

function flatten($data, $prefix = "", $item_seperator = "/") {
    $seperator = $prefix == "" ? "" : $item_seperator;
    $return = array();
    if (is_array($data)) {
        foreach($data as $key => $value) {
            $return[$value["endeca_id"]] = $prefix . $seperator . $value["url_key"];
            if(array_key_exists("children", $value))
            {
                $return = $return + call_user_func(__FUNCTION__, $value["children"], $prefix . $seperator . $value["url_key"], $item_seperator);
            }
        }
    }
    return $return;
}

Answer 1

I liked this challenge, this should do it:

<?php
$start = array(
    0 => array(
        'parent_id' => null,
        'name' => "Root",
        'children' => array(
            10 => array(
                'parent_id' => 0,
                'name' => "Category A",
                'children' => array(
                    30 => array(
                        'parent_id' => 10,
                        'name' => "Category C"
                    )
                )
            ),
            20 => array(
                'parent_id' => 0,
                'name' => "Category B"
            )
        )
    )
);

function recurse($data, $prefix = '') {
    $seperator = ($prefix == '' ? '' : ' > ');
    $return = array();
    if (is_array($data)) {
        foreach($data as $key => $value) {
            $return[$key] = $prefix . $seperator . $value['name'];
            $return = array_merge($return, recurse($value['children'],$prefix . $seperator . $value['name']));
        }
    }

    return $return;
}

print_r(recurse($start));
?>