Código PHP:
<?
define('inc_defecto', 'include1.php');
if (!empty($_GET['inc'])){
$inc = $_GET['inc'];
}
else{
$inc = inc_defecto;
}
if (!empty($inc))
{
echo '<form action="index.php" name="form1" class="simple" id="form1">
<select name="inc" size="1" class="simple">
<option value="include1.php">include1</option>
<option value="include2.php">include2</option>
<option value="include3.php">include3</option>
</select></form>
<div align="right">';
include ($inc);
echo '</div>';
}
else {
echo "erro en include";
}
Gracias