Log off and click on the browser back to the landing after the interface

After logging off, click the browser back and back to the login interface
There are three interface logon.php/checklogon.php/detail.php/logout.php

Logon.php-session_start () and other static HTML including landing form, click on the button to jump to checklogon.php.

checklogon.php-Connect to the database and return user information. If successful $_session[' user ' = information about the users, and jump to detail.php.

$user = Userbusiness::getuser ($_post["username"], $_post["password"]);
if ($user = = null)
{
Header ("Location:/index.php");
Exit
}
$_session[' user '] = $user;

detail.php-A logout link is included above, and logout.php is called when clicked.

Logout.php-

 
  Session_destroy ();
Header ("Cache-control:private, Must-revalidate, No-store");
Header ("Pragma:no-cache");
Header ("Expires:sat, 1997 05:00:00 UTC");
Header ("Location:/logon.php");
Exit ();
?>

When clicked on the Logout button, the page to the landing screen, but click the browser Back button (IE 8/firefox), the previous detail interface is displayed. How can we solve this problem?

When the Back button is clicked, the code inside the detail.php is not executed, and the cached detail.php should be displayed.

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------Solution--------------------
Reference:

   
    Echo (' Logout ');
?>

This is it?
There's no code inside you to verify that the session exists, even if you destroy the session.
------Solution--------------------
To modify the login PHP, add the following code.

!--? php
session_start ();//use session to store user information 
 
 if (isset ($_post["username"))/ /database read username user name 
 {
 $ss _user_id= ""; 
  
//Use the user-tired IsValid () method to determine if the username and password entered are correct 
 require_once ("userclass.php"); The class that gets the user information 
 $user =new User (); 
 If correct, go to the site home page 
 if ($user->isvalid ($_post["username"],$_post["password"], $ss _user_id)) 
 {
 $_session[  ss_user_id "]= $ss _user_id; User ID 
 echo ""; 
} 
//If it is not correct, refresh the page 
 else 
 {
 echo "echo "alert (' Username or password error ');"; 
& #xe63a;