防止在刷新php mysqli上重新提交表单

Question

当我刷新管理面板的表单页面时，给定的信息再次插入数据库表中。这是下面的代码。

<?php

if ($_SERVER["REQUEST_METHOD"]=="POST") {
    if (isset($_POST['sbtn'])) {
        $message = $obj_super_admin->save_hero_info($_POST);
    }
}




?>

，下面给出了数据库代码

<?php

require 'db_connect.php';
class Super_Admin
{
    protected $db_obj;
    public function __construct()
    {
        $this->db_obj = new DB_Connection;
    }
    public function logout()
    {
        unset($_SESSION['admin_id']);
        unset($_SESSION['admin_name']);
        $_SESSION['message'] = "You are Successfully Loged Out";
        header('Location:index.php');
    } 

    public function save_hero_info($data)
    {
        $query = "INSERT INTO title_slogan(title, slogan)" . "VALUES ('$data[title]','$data[slogan]')";
        $this->db_obj ->db_conn->query($query);
        $message="Hero information succesfully saved into database";
        return $message;

    }
}
?>

在主页中调用Super_Admin类。

现在我该怎么办？请帮忙。 提前致谢。