magento2-docker/app/code/IpSupply/SyncOrder/Sync/Buyer.php

<?php
namespace IpSupply\SyncOrder\Sync;

class Buyer implements \JsonSerializable
{
    public $username = '';
    public $fullName = '';
    public $primaryPhone = '';
    public $email = '';

    public function jsonSerialize()
    {
        return get_object_vars($this);
    }
}