Redirect with target="_top" option

I have a web page that is embedded in an iframe on another website. The page has a form with the buttons Cancel and Continue.
On Cancel, I want to address a controller function which destroys the session, after that, the user should be redirected to the top level of the website with the iframe.
Until now, I have this code linked to the Cancel button:

Code:

<a href="....." target="_top">Cancel</a>

But I want to destroy the session before that. Any ideas?
A simple redirect without the target="_top" option will load the whole website inside the iframe.

Create a function/method in a CI helper to destroy the session

PHP Code:

$CI =& getinstance();
$this->CI->session->sess_destroy(); 


What did you Try? What did you Get? What did you Expect?

Joined CodeIgniter Community 2009.  ( Skype: insitfx )

I've found a solution:

PHP Code:

public function cancelled()
{
  $this->session->sess_destroy();
  echo "<script>top.window.location = 'http://the-top-website'</script>";
  die();
}