PHP if not statements

Question

This may be the way my server is set up, but I\'m banging my head against the wall. I\'m trying to say that if $action has no value or has a value that is not \

Answer 1

Not an answer, but just for the sake of code formatting

if((isset($_GET['a'])) $action=$_GET['a']; else $action ="";
if(!($action === "add" OR $action === "delete")){
  header("location: /index.php");
  exit;
}

Note the exit; statement after header(). That's the important thing. header() does not terminate script execution.