Redirect signature verification

Link https://merchant.alikassa.com/cabinet/form/setting-api-certs generate "API certificate for notifications", save the archive, unpack

Wrap all POST data in json (in the same order) and sign

$verif = openssl_verify(json_encode([
    'order_id' => $_POST['order_id'],
    'uuid' => $_POST['uuid'],
]),
    base64_decode($_POST['sign']),
    file_get_contents('./certs/notification/public.pem'));

if (!$verif) {

    throw new \Exception;
}