将JSON对象转换为子对象

Question

I have following JSON object

[{ "item":"foo", "category_id":1 },{ "item":"bar", "category_id": 2},{ "item":"bar", "category_id":3}]

needs to convert as follows:

[{ "item":"foo", "category_id":1 },{ "item":"bar", "related": { "category_id": [2, 3] }}]

I am writing a php function as

$previous = [];
$category = [];
$result = [];


foreach ($jsonData as $element) {

    if (in_array($element['item'], $previous)) {
        $category[] = $element['category_id'];
        $result[] = $category;
    } else {
        $previous[] = $element['item'];
        $result[] = $element;
    }
}
echo json_encode($result);

which gives output as

[{"item":"foo","category_id":1},{"item":"bar","category_id":2},[3]]

but i am not able to get the JSON as sub object. How can i solve it?

Answer 1

If your first item of the array in your object is gonna be the parent node you could access to the first item copy it to the new object and then iterate through the next items extracting the ids and then add them to the "category_id": array