Ho avuto un problema simile poco tempo fà, e ho risolto così :

<html>
<head>
<title>NetLabIT</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<? $page="body.php"; ?>
<? $_GET['link'] = isSet($_GET['link']) ? $_GET['link'] : '';?>
<? $link = $_GET['link']; ?>
<? $page = "$link".".php"; ?>
<body bgcolor="#FFFFFF" leftmargin="10" topmargin="10" marginwidth="5">
<div align="left"><? include("header.php"); ?> </div>
<table>
<tr>
<td valign="top" ><? include("menu.php"); ?></td>
<td width="20"></td>
<td valign="top" align="center"><? include("$page");?></td>
</tr>
</table>






<div align="left"><? include("footer.php"); ?></div>
</body>


</html>


così passando le variabili tramite il get la variabile $page cambia, prova a dare un occhiata a http://www.netlabit.com

ciao ciao