public function referer($default = null, $local = false) {
		if ($ref = $this->env('HTTP_REFERER')) {
			if (!$local) {
				return $ref;
			}
			$url = parse_url($ref) + ['path' => ''];
			if (empty($url['host']) || $url['host'] === $this->env('HTTP_HOST')) {
				$ref = $url['path'];
				if (!empty($url['query'])) {
					$ref .= '?' . $url['query'];
				}
				if (!empty($url['fragment'])) {
					$ref .= '#' . $url['fragment'];
				}
				return $ref;
			}
		}
		return ($default !== null) ? $default : '/';
	}