Sort then reverse Sort

[bluns]

Hi guys, i have a link to sort values by price etc

<td width="10%" class="textbold"><a href="<?php echo $self.'?offset='.$off.'&amp;sort=price'?>">Price</a></td>

$query="SELECT price,2,3 FROM cardata ORDER BY $sort";

this works fine, but i wish to reverse the sort ie by clicking the price link it shows prices from lowest to highest, by clicking the link again i want it to show prices by highest to lowest

Any ideas?

Thanks

[LordShryku]

I usually just pass another variable.

<?php
$url = $self.'?offset='.$off.'&sort=price';
if(!isset($_GET['rev'])) {
   $url .= "&rev=d";
   $way  = "ASC";
}
else {
   $way = "DESC";
}
?>
<td width="10%" class="textbold"><a href="<?php echo $url; ?>">Price</a></td>
<?php
$query="SELECT price,2,3 FROM cardata ORDER BY $sort $way"; 
?>