Domain Access Global variables

Here are a couple of solutions I've used when using the Domain Access module and have needed some domain specific variables. For these examples we'll assume that you are using these two domains - www.site-a.com and www.site-b.com

1) Get the domain machine name

This is the method I prefer and it will print out something like site_a_com or site_b_com.

This is the machine name given to your domain when setup in your Domain Access settings. To find out or set the machine name go to '/admin/structure/domain' and edit a domain - the machine name appears next to the domain name field.

<?php
  $domainGet = domain_get_domain();
  $domain = $domainGet['machine_name'];
  print $domain;
?>

2) Use standard Drupal Global variables

You could use the cookie domain to variable. The below would print out .site-a.com or .site-b.com depending which site you are on:

<?php
  global $cookie_domain;
  print $cookie_domain;
?>

I think you might also be able to use the global $base_root; variable, but will need to check.

3) Use the actual Domain Access variable global $_domain

$_domain is the 'official' global variable for the Domain Access module, but this is rendered as an array so can't be used out-of-the-box. Here is a post describing how you can add it to your template.tpl.php file in order to create a usable global variable. Since the the pervious methods worked for me I've not actually tried it.