Nested array path as variable

Question

I'm working with building associative arrays using recursive function which involves carrying the path through each instance for pushing values to nested array of key

So we feed our function a base array containing 3 keys with empty arrays as values

$fooArray = array(2 => array(), 14 => array(), 8 => array());
$ids = array(2, 14, 8);
function test($fooArray, $ids) {

Our recursive function starts with looping those ids, checking for subids of each and then adding that array filled with values to key

$subids = array(5, 8, 9);
$subkeys = array_fill_keys($subids, array());
$fooArray[$id] = $subkeys;

On the second run of our recursive function, we loop through the newly added sub set of keys and rerun the process. The issue is I'm losing my parent path.

Now I can send our first $id through the function as a parent id and then push

$fooArray[$pid][$id] = $subkeys

But now what do I do for a third and fourth run? What I need is a way to build that path and carry it through each function

$path = $fooArray[$pid][$id];
$path = $fooArray[$pid][$pid][$id];

This is my best attempt

function rcr(&$fooArray, $ids, $path, $i = 0) {
   if ($ids and count($ids) > 0) {
     foreach( $ids as $id ) {
         $subids = // function that gets our array of subids
         $subkeys = array_fill_keys($subids);
         if ($i == 0) {
            $fooArray[$id] = $subkeys;
            $path = &$fooArray[$id];
         } else {
            $path[$id] = $subkeys;
            $path = &$path[$id];
         }
         $s = $i + 1;
         function rcr($fooArray, $subids, $path, $s);
     }
  }
}

function get_rcr() {
   $fooArray = array(2 => array(), 14 => array(), 8 => array());
   $ids = array(2, 14, 8);
   $path = "";
   rcr($fooArray, $ids, $path, $i = 0);
   return $fooArray;
}

But on the second run of the function, $path[$id] fails to add to the main $fooArray

The desired result is

array(
  [2] => array(
      [5] => array(
          [7] => array(
               [46] => array()
          )
      ),
      [108] => array()
  ), 
  [14] => array(),
  [8] => array(
      [72] => array()
  )
)

So how?

Could you make it more explicit what your input is and what result you're looking for? At least some examples. — Jeto, Jan 04 '20 at 09:20
There are a few issues here: you should call rcr in rcr to get recursion, ie remove function keyword from function body. You call rcr in get_rcr without arguments. — PeterM, Jan 04 '20 at 09:23
Also this is invalid syntax (can't have `function rcr($fooArray, $subids, $path, $s);` in the middle of your code, guess that `function` keyword shouldn't be there). — Jeto, Jan 04 '20 at 09:28
Does that matter @Jeto? It comes from another function that gets subids of id — Leopold, Jan 04 '20 at 09:32

Jeto · Accepted Answer · 2020-01-04T09:57:24.833

I'm not entirely sure I understood the question completely, but here goes.

You could make use of a far simpler approach, by only taking an array of IDs as parameter and filling an array where:

each key is the ID,
and each value is the result of the following iteration, based on that ID's sub IDs.

Function:

function rcr(array $ids): array
{
  $array = [];
  foreach ($ids as $id) {
    $array[$id] = rcr(getSubIds($id));
  }
  return $array;
}

Where getSubIds is that other function that gets sub IDs of an ID. Here's a dummy implementation of it following your sample:

function getSubIds(int $id): array
{
  switch ($id) {
    case 2: return [5, 108];
    case 5: return [7];
    case 7: return [46];
    case 8: return [72];
    default: return [];
  }
}

Usage:

$result = rcr([2, 14, 8]);

Demo: https://3v4l.org/tjMRa

Nested array path as variable

1 Answers1