magento 2 I want to write the dynamic {{var shipping_company}} into the xml file

Question

Helllo, i want to set the the dynamic value of variable into xml file

try {
        $om = \Magento\Framework\App\ObjectManager::getInstance();

    $filesystem = $om->get('Magento\Framework\Filesystem');
    $directoryList = $om->get('Magento\Framework\App\Filesystem\DirectoryList');
    $media = $filesystem->getDirectoryWrite($directoryList::MEDIA);

    $contents = '<?xml version="1.0" encoding="utf-8"?>
<TESTORDER>
  <TESTINFO>
    <SHIPADDRESS>
      <NAME>{{var shipping_firstname}} {{var shipping_lastname}}</NAME>
      <ADDRESS1>{{var shipping_company}}</ADDRESS1>
      <ADDRESS2>{{var order.getShippingAddress().getStreet(1)}}</ADDRESS2>
      <ADDRESS3>{{var order.getShippingAddress().getStreet(2)}}</ADDRESS3>
      <ADDRESS4></ADDRESS4>
      <CITY>{{var shipping_city}}</CITY>
      <STATE>{{var order.getShippingAddress().getRegion()}}</STATE>
      <ZIP>{{var shipping_postcode}}</ZIP>
      <COUNTRY>{{var shipping_country_id}}</COUNTRY>
      </SHIPADDRESS>
  </TESTINFO>
</TESTORDER>';
            $media->writeFile("test/test.xml",$contents);
        }
        catch(Exception $e){
        echo $e->getMessage();
    }