protected function _buildOptions($options = []) {
		$gravatarOptions = array_intersect(array_keys($options), array_keys($this->_defaultConfig));
		if (!empty($gravatarOptions)) {
			$optionArray = [];
			foreach ($gravatarOptions as $key) {
				$value = $options[$key];
				$optionArray[] = $key . '=' . mb_strtolower($value);
			}
			return '?' . implode('&amp;', $optionArray);
		}
		return '';
	}