if (!(isset($_POST['fullname']) && strlen($_POST['fullname']))) {

  echo 

  <script type=text/javascript>.

  window.alert('You must enter your full name.');.

  </script>; 



   exit;             

}

The above code is in the register.php file. I have html form in the index.html. when i post the form without full name. it displays alert but page gets stuck at register.php (blank page.)
i want to display the alert on index.html page or atleast get redirected to index.html.
how to do it???