Bagaimana cara menampilkan data SET SARANG hierarkis dengan PHP?

Berdasarkan tautan yang ditunjukkan Stu kepada saya, tutorial menunjukkan kueri ini untuk menentukan kedalaman:

SELECT node.name, (COUNT(parent.name) - 1) AS depth
FROM nested_category AS node,
        nested_category AS parent
WHERE node.lft BETWEEN parent.lft AND parent.rgt
GROUP BY node.name
ORDER BY node.lft

Jadi sesuatu seperti ini seharusnya berhasil:

<?PHP
$query = 'SELECT node.name, (COUNT(parent.name) - 1) AS depth
    FROM nested_category AS node,
            nested_category AS parent
    WHERE node.lft BETWEEN parent.lft AND parent.rgt
    GROUP BY node.name
    ORDER BY node.lft';

$result = mysql_query($query, $db) or die (mysql_error($db));
while ($row = mysql_fetch_assoc($result)) {
    for ($i = 0; $i < $row['depth']; $i++) {
        echo '==>';
    }

    echo $row['name'];
    echo '<br />';
    echo '<br />';
}
?>

Ini akan menghasilkan:

Saws
==>Chainsaws
==>==>Red
==>==>Yellow
==>Circular Saws
==>Other Saws