Order by php et mysql

if(isset($_GET['ordre']) && $_GET['ordre']=='ville')
{
$sql='SELECT * FROM table ORDER BY ville ASC';
}
elseif(isset($_GET['ordre']) && $_GET['ordre']=='date')
{
$sql='SELECT * FROM table ORDER BY date ASC';
}
else{$sql='SELECT * FROM table ORDER BY date ASC';}

echo'<table>
<tr><th>Champ</th><th><a href="index.php?page=liste&ordre=date">Date</a></th><th><a href="index.php?page=liste&ordre=ville">Ville</a></th></tr>';


$req = mysql_query($sql) or die('Erreur SQL !<br />'.$sql.'<br />'.mysql_error());
while($data = mysql_fetch_array($req))
{
echo'<tr><td></td><td>'.$data['date'].'</td><td>'.$data['ville'].'</td></tr>';
}
echo'</table>';