Page not redirect after logout in PHP

I have two situation, currently I’m run my script from two different places with same script, first from localhost and second from website. The problem is when I run locally it logout successfully, it will redirect to index.php but why when I run at website it’s not 100% working? The logout function is working but it’s not redirect to index.php, It still appear the same page not index.php page.

My Logout Code as below:

<a href="<?php echo $logoutAction ?>">[Logout]</a>

My Session Code as below:

<?php
//initialize the session
if (!isset($_SESSION)) {
  session_start();
}

// ** Logout the current user. **
$logoutAction = $_SERVER['PHP_SELF']."?doLogout=true";
if ((isset($_SERVER['QUERY_STRING'])) && ($_SERVER['QUERY_STRING'] != "")){
  $logoutAction .="&". htmlentities($_SERVER['QUERY_STRING']);
}

if ((isset($_GET['doLogout'])) &&($_GET['doLogout']=="true")){
  //to fully log out a visitor we need to clear the session varialbles
  $_SESSION['MM_Username'] = NULL;
  $_SESSION['MM_UserGroup'] = NULL;
  $_SESSION['PrevUrl'] = NULL;
  unset($_SESSION['MM_Username']);
  unset($_SESSION['MM_UserGroup']);
  unset($_SESSION['PrevUrl']);

  $logoutGoTo = "index.php";
  if ($logoutGoTo) {
    header("Location: $logoutGoTo");
    exit;
  }
}
?>

Answer

Finally, I found it by myself, the simple code that I found is:

<?php
session_start(); //Start the current session
session_destroy(); //Destroy it! So we are logged out now
header("location:index.php?msg=logout");
?>

Anyway, thanks to all of you that want to try to help me.