Recursively extract key paths from array - excluding numeric keys and First parent

Question

Please refer my question,

Recursively extract key paths from array - excluding numeric keys

   <?php
$array=json_decode('{"orders": [
{"client":"4","gateWay":"1","store":"store.shop.com","valid":"true","po":34535,"additionalPO":23423,"customerNotes":"","orderItems":[{"item":"123","quantity":10,"supplierLotNo":"","customsValue":"","customsDescription":"","hsCode":""},{"item":"345","quantity":50}],"shippingInfos":[{"address":{"city":"Chennai","country":"India","postalCode":"86715","state":"TN","streetAddress1":"6971 North Street","streetAddress2":null},"contact":{"company":null,"email":"info@store.com","firstName":"test","lastName":"test","phoneNo":null},"ServiceId":"3","thirdPartyAccountNo":"","signatureConfirmation":false,"saturdayDelivery":false}]}]}',true);

function getUniqueObjectKeyPaths(array $array, $parentKey = "") {
    $keys = [];
    foreach ($array as $parentKey => $v) {
        if (!is_numeric($parentKey) && !is_array($v)) {
            $keys[] = $parentKey;
        }
        if (is_array($v)) {
            $nestedKeys = getUniqueObjectKeyPaths($v, $parentKey);
            foreach($nestedKeys as $index => $key) {
                if (!is_numeric($parentKey) && !is_numeric($key)) {
                    $nestedKeys[$index] = $parentKey . "->" . $key;
                }
            }
            $keys = array_merge($keys, $nestedKeys);
        }
    }
    return $keys;
}
$k=getUniqueObjectKeyPaths($array);
print_r($k);
?>

I changed the above function to work for my requirement,

    function getUniqueObjectKeyPaths(array $array, $parentKey = "") {
        $keys = [];
    $i=0;
        foreach ($array as $parentKey => $v) {
            if (!is_numeric($parentKey) && !is_array($v)) {
                $keys[] = $parentKey;
            }
            if (is_array($v)) {
    if($i==0)
    $parentKey="";
                $nestedKeys = getUniqueObjectKeyPaths($v, $parentKey);
                foreach($nestedKeys as $index => $key) {
                    if (!is_numeric($parentKey) && !is_numeric($key)) {
                        $nestedKeys[$index] = $parentKey . "->" . $key;
$keys[] = $parentKey;
                    }
                }
                $keys = array_merge($keys, $nestedKeys);
            }
    $i++;
        }
        return $keys;
    }

my output is,

Array ( [0] => orders->client [1] => orders->gateWay [2] => orders->store [3] => orders->valid [4] => orders->po [5] => orders->additionalPO [6] => orders->customerNotes [7] => orders->orderItems->item [8] => orders->orderItems->quantity [9] => orders->orderItems->supplierLotNo [10] => orders->orderItems->customsValue [11] => orders->orderItems->customsDescription [12] => orders->orderItems->hsCode [13] => orders->orderItems->item [14] => orders->orderItems->quantity [15] => orders->shippingInfos->address->city [16] => orders->shippingInfos->address->country [17] => orders->shippingInfos->address->postalCode [18] => orders->shippingInfos->address->state [19] => orders->shippingInfos->address->streetAddress1 [20] => orders->shippingInfos->address->streetAddress2 [21] => orders->shippingInfos->contact->company [22] => orders->shippingInfos->contact->email [23] => orders->shippingInfos->contact->firstName [24] => orders->shippingInfos->contact->lastName [25] => orders->shippingInfos->contact->phoneNo [26] => orders->shippingInfos->ServiceId [27] => orders->shippingInfos->thirdPartyAccountNo [28] => orders->shippingInfos->signatureConfirmation [29] => orders->shippingInfos->saturdayDelivery )

But my expected output is,

I need orders as one key,instead of orders->shippingInfos->saturdayDelivery i need only shippingInfos->saturdayDelivery.ie. skip first parent if second parent is array or object.

how can i achieve this,