php header cannot redirect

I have implemented a simple signup page,which after the user has signed up must re-direct them to the thank you page, here is my code and it returns a blank page

'
save.php

'

   if($mail->Send()) {}

    unset($_SESSION['GENRE_REQUEST']);

    }
    header('Location:thanku.php');
        exit();
    }

    else
        {
        header('Location:thanku.php');
        exit();
        } '

---

thanku.php

 
       Thank You for Registering With us. 
        
please activate your profile by clicking on the activation link sent to your email address.
       
   'a
                      '