Please help--PHP logout

[Anon]

Hi everyone,
I am using PHP to create the login and logout function in my website. I am using the "session" method. It seems that login works well, but the logout does have the problem. I can always use the "back" button in the browser to get back to the private site. Although when I clicked the "back" button, I got the "expired" information as I expected, as long as I clicked the "refresh" button, the private site would appear again.
Could anybody tell me what the wrong is here? Thank you so much!

Rong

My login.php:
<?
session_start();

if($name && $pass)
{
require("lib/connect.inc");
$query="select count(*) from auth where user='$name' and pass =
password('$pass')";
$result=mysql_query($query);
require("lib/runquery.inc");
$result=mysql_query($query);

if(mysql_result($result,0,0)>0)
{
$valid_user=$name;
session_register("valid_user");
}
}
if(session_is_registered("valid_user")){
require("private.html");
}

else
{
if (isset($name))
echo "<h2>You enter the incorrect username or password. Please
retry.</h2><br>";
else
echo "<h2>You are not logged in.</h2><br>";
}

My logout.php:
<?
session_start();

$old_user=$valid_user;
$result=session_unregister("valid_user");
$destroy= session_destroy();

if (!empty($old_user))
{
if($result && $destroy)
require("home.html");
else
echo "<h2>could not log you out.</h2>";
}

else
echo "<h2> You were not logged in, and so have not been logged
out.</h2>";
?>

[Anon]

u can disable caching on each page. but it seems can't work on IE.

[Anon]

Here is the login/logout script I use on my website for users. It's one file and it is called user_login.php. To logout, just set the link to /user_login.php?action=logout and it logs the user out. This script does not give you the option to refresh the session. At least when I tried it didn't for me. I'm using IE 5.5.

<?

if ($action == "login") {
	//Select User from database
		$db_name = "DBNAME HERE";
		$table_name = "member_list";
		$connection = @mysql_connect ("$host", "$user", "$pass") or
				die ("Couldn't Connect!");
		$db = @mysql_select_db ($db_name, $connection) or
				die ("Couldn't Select Database!");
		$sql = "
					SELECT id, alias, password
					FROM $table_name
					ORDER BY id
		";
		$result = @mysql_query ($sql, $connection) or
				die ("Couldn't Execute Query!");

		while ($row = mysql_fetch_array ($result)) {
			$table_id = $row['id'];
			$alias = $row['alias'];
			$password = $row['password'];
			if ($alias == $login_user) {
				break;
				}
		}

	if ($alias == $login_user && $password == $login_password) {
		//Starts a session
		session_start();
		session_register('valid', 'user_id', 'user_id_check');
		$id = $table_id;
		$valid = "yes";
		$user_id = $table_id;
		$user_id_check = $user_id;
		header("Location: http://www.sidewinderlan.com/main.php?subject=news&user=$id");
	} else {
		$valid = "no";
		header("Location: http://www.sidewinderlan.com/main.php?subject=news");
	}
} 


if ($action == "logout") {
	session_start();
	session_destroy();
	header("Location: http://www.sidewinderlan.com/main.php?subject=news");
}

?>

Hope that helps.

Jaryd