Last row inserted to be displayed first

I have the following PHP script :

<?php
header('Content-type: text/xml');

mysql_connect('localhost', 'root', 'root');

mysql_select_db('sportApp');

if ($_REQUEST['past']) {
    $result = mysql_query('SELECT * FROM chatitems WHERE id > ' . mysql_real_escape_string($_REQUEST['past']) . ' ORDER BY added LIMIT 50');
} else {
    $result = mysql_query('SELECT * FROM chatitems ORDER BY added LIMIT 50');
}
?>
<chat>
    <?php
    while ($row = mysql_fetch_assoc($result)) {
        ?>
        <message added="<?php echo( $row['added'] ) ?>" id="<?php echo( $row['id'] ) ?>">
            <user><?php echo( htmlentities($row['user']) ) ?></user>
            <text><?php echo( htmlentities($row['message'])) ?></text>
            <subtext><?php echo( htmlentities($row['subtext'])) ?></subtext>
            <image><?php echo( htmlentities($row['image']) ) ?></image>
            <ytvideo><?php echo( htmlentities($row['ytvideo']) ) ?></ytvideo>
        </message>
        <?php
    }
    mysql_free_result($result);
    ?>
</chat>

I have stored on my localhost and MYSQL table with seven elements,one of they is an TIMESTAMP,when i insert a new row the time is saved.The question is how can i order my displaying page by the last rows added [ I Want the last row inserted to be displayed first, see the code]. Help please!

Copyright Notice：Content Author:「Jamal Tyson」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/7458059/last-row-inserted-to-be-displayed-first