Well, first you should see
Secure Sessions in PHP[
^]
When the user logs in, save the username in a session. Like so
secure_session_start();
$_SESSION['name'] = sanitized_username;
$_SESSION['login_key'] = user_login_key;
?>
<html>
<head>
<title>My document title</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<link rel="stylesheet" href="Styles/header_main.css">
</head>
<body>
<div class="wrapper col0">
<div id="topline">
<p>Welcome, <?php echo $_SESSION['name'];?>!</p>
<ul>
<li><a href="#">CHANGE PASSWORD</a></li>
<li class="last"><a href="logout.php">LOGOUT</a></li>
</ul>
<br class="clear" />
</div>
</div>
<div id="container">
</div>
</body>
</html>