如何在GET URL上重定向页面

Question

I have a page like this index.php?controller=a&action=b, but on this page controller=a i did nothing, if i access it just a blank page. I need to redirect from controller=a to original page controller=a&action=b?

Answer 1

What if just check the page url and redirect,

if(isset($_GET['controller']) && $_GET['controller'] == "a"){
    header("location: index.php");
}