Drupal Default Site Redirection Template

default-site-redirect.settings.php

<?php

/**
 * Redirection rules for default Drupal site
 *
 * This drop-in for the default site's settings.php provides HTTP 301
 * redirection rules for any request which does not already have a Drupal
 * site folder assigned. Redirect rules are located in the global
 * default_redirect array.
 *
 * Redirects are selected in the following manner:
 * 1. HTTP_HOST and REQUEST_URI combined to look for an exact match in
 *    default_redirect
 * 2. If not found, look for the full HTTP_HOST in default_redirect
 * 3. Then iterate through progressively more abstract hostname parts until
 *    match is found.
 * 4. Default site redirect is used if no other is found.
 *
 * Example Request: http://aa.bb.example.localhost/some/path
 *
 * - looks for match to 'aa.bb.example.localhost/some/path'
 * - looks for match to 'aa.bb.example.localhost'
 * - looks for match to 'bb.example.localhost'
 * - looks for match to 'example.localhost'
 * - looks for match to 'localhost'
 *
 * To use this file to redirect traffic, append or include this file at the
 * bottom of sites/default/settings.php. For example:
 *
 *   require_once('default-site-redirect.settings.php');
 *
 * Edit the following defined variables as needed.
 *
 * DEFAULT_SITE_REDIRECT - if this is blank, the default drupal site will load
 * DEFAULT_SITE_DRY_RUN - when true, adds mock-headers instead of redirecting
 *
 * Note: in all cases, the SERVER_PORT is dropped from the request's HTTP_HOST
 */

define('DEFAULT_SITE_REDIRECT', '');
define('DEFAULT_SITE_DRY_RUN', TRUE);

$GLOBALS['default_redirect'] = array (
  'b.cc.example.localhost/a-specific-url.html' => 'example-destination.localhost:8082/redirect/rule/0',
  'aa.bb.cc.example.localhost' => 'example-destination.localhost:8082/redirect/rule/1',
  'bb.cc.example.localhost' => 'example-destination.localhost:8082/redirect/rule/2',
  'cc.example.localhost' => 'example-destination.localhost:8082/redirect/rule/3',
  'example.localhost' => 'example-destination.localhost:8082/redirect/rule/4',
);

/**
 * Select the most specific matching pattern for the given hostname
 */
function default_site_select_redirect() {

  global $default_redirect;
  $location = DEFAULT_SITE_REDIRECT;

  // Sanitize and trim the HTTP_HOST
  $http_host = preg_match('/^([a-zA-Z0-9_\-\.]+)(\.)?(:[0-9]+)?$/',$_SERVER['HTTP_HOST'], $matches) ? $matches[1] : 'default';

  // Lookup the exact request, incuding URI
  $request = $http_host . $_SERVER['REQUEST_URI'];
  if (isset($default_redirect[$request])) {
    $location = $default_redirect[$request];
  }
  // Iterate through progressively more abstract hostnames
  else {
    $server = explode('.', $http_host);
    for ($j = count($server); $j > 0; $j--) {
      $pattern = implode('.', array_slice($server, -$j));
      // Lookup the partial request, break on the first match
      if (isset($default_redirect[$pattern])) {
        $location = $default_redirect[$pattern];
        break;
      }
    }
  }
  return $location;
}

/**
 * Handle default site requests
 */
function default_site_request_handler() {

  if ($location = default_site_select_redirect()) {
    if (!DEFAULT_SITE_DRY_RUN) {
      drupal_add_http_header('Location', 'http://' . $location);
      drupal_add_http_header('Status', '301 Moved Permanently');
      exit;
    }
    else {
      drupal_add_http_header('X-Dry-Run-Location', 'http://' . $location);
      drupal_add_http_header('X-Dry-Run-Status', '301 Moved Permanently');
    }
  }
}

default_site_request_handler();

may need something like drupal_add_http_header('Cache-Control', 'public, max-age=1209600'); for some varnish implementations

Constants cannot be empty.

The current code causes a PHP notice and in some cases can cause a fatal error.

http://www.php.net/manual/en/function.constant.php#98087