How to convert Hierarchical from array to single array

Question

I have a data in below JSON format.

$strTree = '{"id":"1","children":[{"id":"316","children":[{"id":"336","children":[{"id":"423"}]},{"id":"337","children":[{"id":"418"}]},{"id":"420"}]},{"id":"405"},{"id":"421"}]}';

And Now I have to build new array using this data for identifying reporting manager

$strTree = [
    '316' => '1',
    '405' => '1',
    '421' => '1',
    '336' => '316',
    '337' => '316',
    '420' => '316',
    '418' => '337',
    '423' => '336',
]

Here What I have tried, but didn't find out the solution to get the expected result

$strTree = '{
    "id": "1",
    "children": [{
        "id": "316",
        "children": [{
                "id": "336",
                "children": [{"id": "423"}]
            },
            {
                "id": "337",
                "children": [{"id": "418"}]
            }, {"id": "420"}
        ]
    },
    {"id": "405"},
    {"id": "421"}
]}';
$arr = (array) json_decode($strTree);
$arrHierarchicalEmpDetails = buildResultedArray($arr, 1);

function buildResultedArray( $elements, $parentId = 0) {
    $branch = [];
    $elements = (array) $elements; 
    foreach ($elements as $element) {
        $element = (array) $element;
        $intID = $element['id'];
        $branch[ $intID ] = $parentId;
        if (!empty( $element['children'])) {
            buildTree( $element['children'], $element['id']);
        }
    }
    return $branch;
}
echo '<pre>'; print_r($arrHierarchicalEmpDetails);

$arr = json_decode($strTree, true); will give you an array, if you dont like using objects. — RiggsFolly
– RiggsFolly, Commented Sep 27, 2018 at 13:33
@RiggsFolly I have converted that JSON into an array, but am unable yo prepare expected array from the converted array. — Gajanan Kolpuke
– Gajanan Kolpuke, Commented Sep 27, 2018 at 13:35

Ezequiel De Luca · Accepted Answer · 2018-09-27 14:44:28Z

1

Gerber, to solve this problem, you could use a recursive function to "flatten" the hierarchical array:

function flattenHierarchicalArray($inputArray, $parentId = null)
{
    $flattenedData = [];
    if (!empty($inputArray['children'])) {
        foreach ($inputArray['children'] as $child) {
            $flattenedData += flattenHierarchicalArray($child, $inputArray['id']);
        }
    }

    if (!is_null($parentId)) {
        $flattenedData[$inputArray['id']] = $parentId;
    }

    return $flattenedData;
}

You should call the function on this way:

flattenHierarchicalArray($data)

Where $data is the hierarchical array decoded from your JSON example. Output:

array(8) {
  [423]=>
  string(3) "336"
  [336]=>
  string(3) "316"
  [418]=>
  string(3) "337"
  [337]=>
  string(3) "316"
  [420]=>
  string(3) "316"
  [316]=>
  string(1) "1"
  [405]=>
  string(1) "1"
  [421]=>
  string(1) "1"
}

Note: this function does not keep the order of your expected output, I've asumed that wasn't important at all.

answered Sep 27, 2018 at 14:44

Ezequiel De Luca

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2 Comments

Gajanan Kolpuke Over a year ago

I just modified $inputArray [ $inputArray = (array) $inputArray ] type to array & it works for me. Thanks a lot.

Ezequiel De Luca Over a year ago

@GajananKolpuke you're welcome. To avoid the cast of the $inputArray variable, you could pass true as the second parameter of json_decode. With that parameter json_decode returns an associative array instead of a PHP StdObject.

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