If you want to do conditional includes then you should just add a check to see if the user is logged in and include the file if they are. I don’t know how you implemented the login and authentication stuff but based on the info you provided it would be like so:
<body>
<?php include('lock.php');
if($login_session != 'admin') { // or however else you would check the login status
echo "<h1> Please Log In </h1>";
} else {
include('hostess.php'); // include and display all the rest of the stuff
// display the stuff
?>
<div id="menu">
<ul>
<li><a href="https://stackoverflow.com/questions/11052579/logout.php">log out</a></li>
</ul>
</div>
<h1> Welcome <?php echo $login_session; ?> </h1>
<?php } // close else ?>
</body>
solved Quick thing, make file accessible only by admin, php