What will be the alternative of arrayObject()?

Question

During migration of my code from PHP5 to PHP7, I am facing some pretty issues, One of them are arrayObject(). arrayObject in PHP7 is not behaving as expected, what will be the alternate solution to achieve arrayObject functionality.

//I have some data in this carList array
$carList = array();  

$carArray = new ArrayObject();

//Go throuch each car record and populate the car object
foreach ($carList as $lst){
    $car = new carDetail();
    foreach ($lst as $key=>$value){
        $car->{lcfirst($key)} = $value;
    }

    $car = new SoapVar($car, SOAP_ENC_OBJECT, null, null, 'car');
    $carArray->append($car);
}
return $carArray;

It results in following Soap Envelope

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://logistics.website.eu">
    <SOAP-ENV:Body>
        <ns1:OutgoingNoosGoodsOrder>
            </carArray>
        </ns1:OutgoingNoosGoodsOrder>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Before migration, it is like this on PHP 5

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://logistics.website.eu">
    <SOAP-ENV:Body>
        <ns1:OutgoingNoosGoodsOrder>
            <carArray>
                 <car>
                   <make> Hyundai </make>
                   <model> Verna </model>
                   <year> 2019 </year>
                 </car>
                 <car>
                   <make> Audi </make>
                   <model> Q7 </model>
                   <year> 2022 </year>
                 </car>
            </carArray>
        </ns1:OutgoingNoosGoodsOrder>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Answer 1

I tried running the following code in https://sandbox.onlinephpfunctions.com/ with PHP 7.4.28 and 5.6.40 :

<?php
class carDetail{}
const car = '3';
$carList = [
  "something" => [1,2,3],
    "another" => [4,5,6],
    "yet_another" => [7,8,9]
];

$carArray = new ArrayObject();

//Go throuch each car record and populate the car object
foreach ($carList as $lst){
    $car = new carDetail();
    foreach ($lst as $key=>$value){
        $car->{lcfirst($key)} = $value;
    }

    $car = new SoapVar($car, SOAP_ENC_OBJECT, null, null, car);
    $carArray->append($car);
}
var_dump($carArray);

?>

The results are exactly the same in PHP 7.4.28 and 5.6.40 (screenshot below):

So the problem must be something else, and not how ArrayObject works.

---

If I were to guess, one thing that stopped working when migrating from PHP5 to PHP7 was:
using an empty string to initialize an array. Like

$myVar = ''; 
$myVar['key']=[1,2,3];

That doesn't work in PHP7, even though it does in PHP5.