elseif($action == 'checkusername') {

                $username = trim($username);

                $guestexp = '\xA1\xA1|^Guest|^\xD3\xCE\xBF\xCD|\xB9\x43\xAB\xC8';
                $censorexp = '/^('.str_replace(array('\\*', "\r\n", ' '), array('.*', '|', ''), preg_quote(($censoruser = trim($censoruser)), '/')).')$/i';
                if(preg_match("/^\s*$|^c:\\con\\con$|[%,\*\"\s\t\<\>\&]|$guestexp/is", $username) || ($censoruser && @preg_match($censorexp, $username))) {
                        showmessage('profile_username_illegal');
                }

                $query = $db->query("SELECT uid FROM {$tablepre}members WHERE username='$username'");
                $username = dhtmlspecialchars(stripslashes($username));

                if($db->num_rows($query)) {
                        showmessage('register_check_found');
                }