如何在我的php语句中正确执行此javascript？

Question

The following code will only be called when a session has timed out. I basically want to display a confirm dialog with javascript to make the user pick if he wants to remain online or not. My problem is that the php that closes the session inside the javascript seems to be executed even if the confirm is true.

if (isset($_SESSION['username']) && isset($_SESSION['last_activity']) && (time() - $_SESSION['last_activity'] > 5)) {
    ?>
    <script type="text/javascript">
    if (confirm("You were logged off due to inactivity, if you would like to remain logged in click OK.")) {
        header("Location:/");
    } else {
    <?php
    connect();
    if(!connect()) {
        die('Could not connect: ' . mysql_error());
        header( "refresh:3; url=/index.php" );
    }
    mysql_select_db('www');
    $user = $_SESSION['username'];
    mysql_query("UPDATE users SET online='0'
    WHERE username='$user'");
    session_unset();
    session_destroy();
    ?>
    }
    </script>
<?php
}
$_SESSION['last_activity'] = time(); // update last activity time stamp
?>

Answer 1

The PHP code is run before the page is loaded by the browser. JavaScript is run after the page is loaded by the browser. You cannot just mix them like this and expect everything to somehow happily work. See HTTP, AJAX and WebSockets.