codice:
if (!isset($_GET['id']))
	$sql="SELECT * FROM tabella HAVING id = MIN(id)";
else
	$sql="SELECT * FROM tabella WHERE id > {$_GET['id']} LIMIT 1";
$st=mysql_query($sql) or die(mysql_error());
$row=mysql_fetch_assoc($st);
echo $row['id']." ".$row['campo1']." ".$row['campo2'];
echo "<a href=\"{$_SERVER['PHP_SELF']}?id={$row['id']}\">prossimo</a>\n";