Better TwiML Echo

echo.php

<?php
header('Content-Type: text/xml');

$result = $_GET['Twiml'];
foreach($_REQUEST as $k => $v) {
  if ($k === 'Twiml') { continue; } // avoid infinite loop
  $result = str_replace('${' . $k . '}', $v, $result);
}//end for: replaced all the tokens

echo $result;