if(isset($_POST['uname']) && isset($_POST['password'])){
    $logged = login($_POST['uname'],$_POST['password']);
    if($logged){
        header( 'Location: index.php' ) ;
        exit();
    }
}

function login($uname,$password){
    $user = check_db_user($uname,$password)
    if($user){
        session_regenerate_id(TRUE);
        $_SESSION["name"] = $user->name;
        ...
        return true;
    }else{
        return false;
    }
}

header("Set-Cookie: PHPSESSID=" . session_id() . "; path=/");