PHP Recursive JSON Children Search

Question

I need to parse JSON which looks like this:

{
    "mdfId":"282088127",
    "mdfConcept":"ME 3400EG-12CS-M Switch",
    "children":[
        {
            "mdfId":"007",
            "mdfConcept":"Another item",
            "children": [
                // many more here
            ]
        },
        {
             "mdfId":"008",
             "mdfConcept":"Another one",
             "children": [
                 {
                     "mdfId":"010",
                     "mdfConcept":"What I'm looking for!",
                     "children": [] // no children
                 }
             ]
        },
        // many more here
    ]
},

This is a recursive structure in which every element has mdfId , mdfConcept and children keys.

Say I need to find node with ID=010 within this structure. I don't know at which level it lies (eg it can be on top level, or several children nodes below).

My current approach is:

$mdfId = '010'; // what I'm loking for

foreach ($jsonResponse as $category) {
    while (true) {
        if ($category['mdfId'] == $mdfId) {
            // we found it!
            $categoryDevices[$mdfId] = $category['children'];
            break 2;
        }

        if (!empty($category['children'])) {
            next_cat:

            if (is_null($category['children'])) {
                break;
            }

            $category = array_shift($category['children']);
            continue;
        }

        if (empty($category['children'])) {
            goto next_cat;
        }
    }
}

But current approach misses some cases. How can I optimize this recursive loop so it checks all nodes on same level and each one accesible through any number of children keys?

Answer 1

An embarrassing feature of your JSON object is that, while each children member is an array of the "child" structure, the top level one is the object itself , so it's an obstacle to a really recursive approach.

We might workaround by turning the source JSON object into the same structure as nested levels, ie:

• having $jsonResponse as original object
• use ['children' => $jsonResponse] instead

This way, it should work with something like this:

$mdfId = '010'; // what I'm loking for

if ($result = look4id(['children' => $jsonResponse], $mdfId) {
    $categoryDevices[$mdfId] = $result;
}

function look4id($source, $id) {
    foreach ($source as $child) {
        if ($child['mdfId'] == $id) {
            return $source['children'];
        } else {
            if ($source['children']) {
                return look4id($source['children'], $id);
            }
        }
    }
}

Answer 2

So basically I wrote a function that didn't return anything, but rather populated a variable from arguments.

function findRecursiveArrayNodeById($id, $array, &$node) {
    foreach ($array as $child) {
        if (isset($child['mdfId']) && $child['mdfId'] == $id) {
            $node = $child;
            return;
        }

        if (!empty($child['children'])) {
            findRecursiveArrayNodeById($id, $child['children'], $node);
        }
    }
}

Usage as follows:

$result = false;

findRecursiveArrayNodeById($mdfId, $category_json, $result);

if (!$result) {
    println("did not find {$mdfId}");
    continue;
}