public static function authenticate($username, $password)
 {
     if (empty($username) || empty($password)) {
         return NULL;
     }
     //TODO sql escape
     $SQL = "SELECT * FROM " . TBL_ADMIN_USERS . "  WHERE userName='******' AND userPassword='******'";
     $query = mysql_query($SQL, DBUtils::getManualConnection());
     if (empty($query)) {
         return NULL;
     }
     while ($db_field = mysql_fetch_assoc($query)) {
         $admin_user = AdminUsersModel::createAdminUserWithSQL($db_field);
         if (!empty($admin_user)) {
             return $admin_user;
         }
     }
     return null;
 }