public function param($param, $value) {
		if ($value !== null) {
			$param = rawurlencode($param);
			$value = rawurlencode($value);
			$this->params[$param] = $value;
		} else {
			if (isset($this->params[$param])) {
				unset($this->params[$param]);
			}
		}
		return $this;
	}