如何防止用户在登录后访问登录页面？

Question

I want to prevent user to access login page when its already logged in. In header page I've checked session so that user can't access any admin page without logging in. What code do I have to write in header page and session page to prevent user access login page while already logged in?

Here's my session class

public static function init(){
    session_start();
}
public static function set($key, $val){
    $_SESSION[$key]=$val;
}
public static function get($key){
    if (isset($_SESSION[$key])) {
        return $_SESSION[$key];
    } else {
        return false;
    }
}
public static function checkSession(){
    self::init();
    if (self::get("login")==false) {
        self::destroy();
        header("Location:login.php");
    }  
}

public static function destroy(){
    session_destroy();

Answer 1

Check the session variable value on login page if exist then redirect or dashboard or home page if not exist session variable value redirect on login page.