带弹出/重定向的PHP

I have a problem with my PHP code and I don't know if there is an easy fix to what I am trying to accomplish. I have a contact page and I would like to press the submit button, then have it display a message on a new page, then once I press some sort of "ok" button, have the page redirect me to my index page. So far, I was only able to get the redirect to work.

<?php

$redirect_page = 'index.html';
$redirect = True;
if ($redirect==True) {
    header('Location: '.$redirect_page); exit();
}

?>