//for display of categories
$query_categories = mysql_query("SELECT * from tb_categories order by category asc");
while($row_categories = mysql_fetch_array($query_categories))
{
?>
//for display of sub categories
$query_subcategories = mysql_query("SELECT * from tb_sub_categories where category='$row_categories[category]'");
while($row_subcategories = mysql_fetch_array($query_subcategories))
{
?>