Redirect all prod Drupal access to dev or alt environment

pantheon-redirect-all-admin.php

// Redirect user/admin pages to dev site while we are in active dev
/*
if  ((
      $_ENV['PANTHEON_ENVIRONMENT'] === 'live' || 
      $_ENV['PANTHEON_ENVIRONMENT'] === 'test'
    ) && (
      (strpos($_SERVER['REQUEST_URI'], '/user') !== false) || 
      (strpos($_SERVER['REQUEST_URI'], '/admin') !== false)
    )) {
  echo 'https://'. $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
  header('HTTP/1.0 301 Moved Permanently');
  header('Location: https://dev-cua.pantheonsite.io/');
  if (extension_loaded('newrelic')) {
    newrelic_name_transaction("redirect");
  }
  exit();
}
*/