Output ordered by

Output ordered by

I have a table that puts all of the information from my database on a
page. I want to add a drop down that says order by first name, last name,
group, etc...
How do I accomplish this?
<?php $query = "SELECT * FROM contacts WHERE type = 'lead'";
$result = mysql_query($query);
if (!$result) {
die('Invalid query: ' . mysql_error()); } ?>
<table>
<tr><td>ID</td> <td>Name</td> <td>Email</td></tr>
<?php
while ($row = mysql_fetch_assoc($result))
{
echo '<tr>';
echo '<td>' . $row['id'] . '</td>';
echo '<td>' . $row['name'] . '</td>';
echo '<td>' . $row['email'] . '</td>';
echo '<td>' . '<a href = "/admin/leads/convert-contact.php?id=' .
$row[id] . '">Make Contact</a>';
echo '</tr>';
}
echo '</table>';
?>