protected function fetchSregAttributes()
    {
        $attributes = [];
        $sregToAx = array_flip($this->axToSregMap);
        foreach ($this->data as $key => $value) {
            $keyMatch = 'openid_sreg_';
            if (strncmp($key, $keyMatch, strlen($keyMatch))) {
                continue;
            }
            $key = substr($key, strlen($keyMatch));
            if (!isset($sregToAx[$key])) {
                // The field name isn't part of the SREG spec, so we ignore it.
                continue;
            }
            $attributes[$sregToAx[$key]] = $value;
        }

        return $attributes;
    }