login using time

[ravi951]

hi all,
i have database namely shopping for login with 3 fields
namely id,username and password as shown below


create table login(id auto increment primary key,username varchar(20),password varchar(30));

it will be shown as
id username password
1 admin admin123
2 ravi ravi123

i have also written a code in php so that when ever the new user enters using the time function it should
be stored in the database
below is he code....


<?php
if (!isset($_SESSION))
{
session_start();
}
$now = time();
// time the session should have expired
$limit = $now;
// check the time of the last activity
if (isset($_SESSION['last_activity']) && ($_SESSION['last_activity'] < $limit))
{
// clear the session array
$_SESSION = array();
header('Location:logout.php');
exit;
}
else
{
// the current time
$_SESSION['last_activity'] = $now;
}
?>

tell me how to modify the above code so that when the new user logins that must be stored in the login table.....