double click sort ทำไงอะคับ คือเรียก db ขึ้นมาแสดงแล้ว จะทำยังไง ให้ double click ที่หัว column

<a href="?sortfield=field1&dir=des">field1 desc</a>
<a href="?sortfield=field1&dir=asc">field1 asc</a>

<a href="?sortfield=field2&dir=des">field2 desc</a>
<a href="?sortfield=field2&dir=asc">field2 asc</a>

<?php

$allow_fields = array('field1','field2');

if ( empty($_GET['sortfield']) || !in_array($_GET['sortfield'], $allow_fields, true) ){
     $sortfield = 'field1';
}

if (empty($_GET['dir']) || $_GET['dir'] == 'asc'){
     $dir = 'asc';
} else {
     $dir = 'desc';
}

$sql = "SELECT * FROM tb ORDER BY $sortfield $dir";

//... display records
?>