Auth_OpenID_Decoder::decode PHP Method

    function decode($query)
    {
        if (!$query) {
            return null;
        }
        $message = Auth_OpenID_Message::fromPostArgs($query);
        if ($message === null) {
            /*
             * It's useful to have a Message attached to a
             * ProtocolError, so we override the bad ns value to build
             * a Message out of it.  Kinda kludgy, since it's made of
             * lies, but the parts that aren't lies are more useful
             * than a 'None'.
             */
            $old_ns = $query['openid.ns'];
            $query['openid.ns'] = Auth_OpenID_OPENID2_NS;
            $message = Auth_OpenID_Message::fromPostArgs($query);
            return new Auth_OpenID_ServerError($message, sprintf("Invalid OpenID namespace URI: %s", $old_ns));
        }
        $mode = $message->getArg(Auth_OpenID_OPENID_NS, 'mode');
        if (!$mode) {
            return new Auth_OpenID_ServerError($message, "No mode value in message");
        }
        if (Auth_OpenID::isFailure($mode)) {
            return new Auth_OpenID_ServerError($message, $mode->message);
        }
        $handlerCls = Auth_OpenID::arrayGet($this->handlers, $mode, $this->defaultDecoder($message));
        if (!is_a($handlerCls, 'Auth_OpenID_ServerError')) {
            return call_user_func_array(array($handlerCls, 'fromMessage'), array($message, $this->server));
        } else {
            return $handlerCls;
        }
    }