Allows wordpress be accessed with via X-Forwarded-Host servername.

forwarded_host.php

<?php

/*
Plugin Name:    Forwarded Host Support
Description:    Allows the blog to be accessed with via X-Forwarded-Host servername.
Author:         blahed
Version:        0.0.1
Author URI:     http://forwardhq.com/
*/

function has_forwarded_host() {
  return array_key_exists('HTTP_X_FORWARDED_HOST', $_SERVER);
}

function forwarded_host() {
  return $_SERVER['HTTP_X_FORWARDED_HOST'];
}

function forwarded_base() {
  $_forwarded_host = forwarded_host();

  return "//$_forwarded_host";
}

function apply_forwarded_host() {
  if ( !has_forwarded_host() )
    return false;

  return forwarded_base();
}

function replace_with_forwarded_host($url, $path = '') {
  if ( !has_forwarded_host() )
    return $url;
  else
    return preg_replace('!https?://[a-z0-9.-]*!', '//' . forwarded_host(), $url);
}

add_filter('pre_option_home', 'apply_forwarded_host');
add_filter('pre_option_siteurl', 'apply_forwarded_host');
add_filter('pre_option_url', 'apply_forwarded_host');
add_filter('stylesheet_uri', 'replace_with_forwarded_host');
add_filter('admin_url', 'replace_with_forwarded_host');

?>