como criar menu dinâmico com submenu com php e mysql

$q = mysql_query("SELECT sec_id, sec_name, sec_group FROM tbl_user_sec ORDER BY sec_id");

// prepare data 
$groups = Array();
while($w = mysql_fetch_assoc($q)) {
  if(!isset($groups[$w['sec_group']])) $groups[$w['sec_group']] = Array();
  $groups[$w['sec_group']][] = $w;
}

// display data
echo "<ul>";
foreach($groups as $group_name => $sections) {
  echo '<li><a href="#">'.$group_name.'</a><ul>';
  foreach($sections as $section) {
    echo '<li><a href="#">'.$section['sec_name'].'</a>';
  }
  echo '</ul></li>';
}
echo "</ul>";