Prueba esto:
Código PHP:
<?php
include ('book_sc_fns.php');
// The shopping cart needs sessions, so start one
session_start();
?>
<html>
<body background = fondo.gif>
</body>
</html>
<?php
do_html_header('Bievenidos al concesionario ');
echo '<p><h3>Elige categoria</h3></p>';
// Obtener categorias de la base de datos
$cat_array = obtener_categorias();
// display as links to cat pages
display_categorias($cat_array);
// if logged in as admin, show add, delete, edit cat links
if(isset($HTTP_SESSION_VARS['admin_user']))
{
display_button('admin.php', 'admin-menu', 'Admin Menu');
}
do_html_footer();
?>