title: Preserving session variables across different domains
body: <p>I'm not sure if this is even possible. </p>
  
  <p>My company has their main site that accept credit cards and other payment information. They also have other sites that are directly related to events we host. For example our main site is something like:</p>
  
  <p><a href="http://www.etm124biz.com">http://www.etm124biz.com</a></p>
  
  <p>But have another site specifically for an annual event:</p>
  
  <p><a href="http://www.etm124annualgala.com">http://www.etm124annualgala.com</a></p>
  
  <p>My 'event' site is handling registration and saves to our database, but our main site handles the credit card processing. With current purchases handled on the main website, sessions are used to pass data to the payment/cc screens. </p>
  
  <p>Without having to change my payment code (to accept, say, $_GET parameters), shouldn't my <code>$_SESSION</code> variables be passing over?</p>
  
  <p>Example:</p>
  
  <pre><code>$_SESSION['s_address1'] = $_POST['address1'];
  $_SESSION['s_address2'] = $_POST['address2'];
  $_SESSION['s_city']     = $_POST['city'];
  $_SESSION['s_state']    = $_POST['state'];
  $_SESSION['s_zip']      = $_POST['zip'];
  
  header('Location: https://www.etm124biz.com/payment.php?oid=' . $oid . '&amp;src=conf&amp;id=' . $seq);
  </code></pre>
  
  <p>My <code>payment.php</code> page looks for the address session variables above.</p>