PHP indexed array to nested associative array

Question

I need to convert simple array to nested array according to specific rules. I've achived it but I'm looking for better solution.

SIMPLE:

array(4) {
  [0]=>
  array(2) {
    ["id"]=>
    string(2) "11"
    ["type"]=>
    int(3)
  }
  [1]=>
  array(2) {
    ["id"]=>
    string(2) "10"
    ["type"]=>
    int(2)
  }
  [2]=>
  array(2) {
    ["id"]=>
    string(1) "1"
    ["type"]=>
    int(1)
  }
  [3]=>
  array(2) {
    ["id"]=>
    string(1) "0"
    ["type"]=>
    int(1)
  }
}

EXPECTED EFFECT:

array(1) {
  [0]=>
  array(2) {
    ["type"]=>
    int(1)
    ["child"]=>
    array(1) {
      [1]=>
      array(2) {
        ["type"]=>
        int(1)
        ["child"]=>
        array(1) {
          [10]=>
          array(2) {
            ["type"]=>
            int(2)
            ["child"]=>
            array(1) {
              [11]=>
              array(2) {
                ["type"]=>
                int(3)
                ["child"]=>
                array(0) {
                }
              }
            }
          }
        }
      }
    }
  }
}

MY SOLUTION (not very satisfying):

$nestedArray = [];
    foreach ($simpleArray as $item)
    {
        if (!empty($nestedArray))
        {
            $array = $nestedArray;
            reset($array);
            $firstKey = key($array);
        }
        $nestedArray[$item['id']]['child'] = $nestedArray;
        $nestedArray[$item['id']]['type'] = $item['type'];
        if (!empty($firstKey))
        {
            unset($nestedArray[$firstKey]);
        }
    }

As I said, I'm looking for more elegant way to achieve that. Rule are very simply: every next item is child of previous.

So tell us: what is "not very satisfying" here? Without that, how do you expect us to suggest something "more satisfying"? — arkascha
– arkascha, Commented Jun 6, 2018 at 20:50
Do the example input and output relate to eachother? I don't see how their values match... Where does the "id" go? If anything, your last paragraph is describing the opposite: every next element is parent of previous (not child)... or what am I missing? — trincot
– trincot, Commented Jun 6, 2018 at 20:53
I do my best, but I think that my solution is very... basic. First array is related to second. First element of first array is the most nested element of second array. — Bejkrools
– Bejkrools, Commented Jun 6, 2018 at 21:03

trincot · Accepted Answer · 2018-06-06 21:08:03Z

2

You could use recursion:

function nest($arr) {
    return count($arr) ? ["type" => array_pop($arr)["type"], "child" => nest($arr)] : [];
}

With your example input, it would look like this:

$simpleArray = [
    ["id" => "11", "type" => 3],
    ["id" => "10", "type" => 2],
    ["id" => "1", "type" => 1],
    ["id" => "0", "type" => 1]
];

function nest($arr) {
    return count($arr) ? ["type" => array_pop($arr)["type"], "child" => nest($arr)] : [];
}

$nested = nest($simpleArray));

$nested will have the following value:

[
    "type" => 1,
    "child" => [
        "type" => 1,
        "child" => [
            "type" => 2,
            "child" => [
                "type" => 3,
                "child" => []
            ]
        ]
    ]
]

edited Jun 6, 2018 at 21:08

answered Jun 6, 2018 at 21:04

trincot

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1 Comment

Bejkrools Over a year ago

That's what I need - recursion. I have to "make friends with it" ;-) Thanks guys!

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