When\When::rrule PHP Method

    public function rrule($rrule)
    {
        // strip off a trailing semi-colon
        $rrule = trim($rrule, ";");
        $parts = explode(";", $rrule);
        foreach ($parts as $part) {
            list($rule, $param) = explode("=", $part);
            $rule = strtoupper($rule);
            $param = strtoupper($param);
            switch ($rule) {
                case "DTSTART":
                    $this->startDate(new \DateTime($param));
                    break;
                case "UNTIL":
                    $this->until(new \DateTime($param));
                    break;
                case "FREQ":
                case "COUNT":
                case "INTERVAL":
                case "WKST":
                    $this->{$rule}($param);
                    break;
                case "BYDAY":
                case "BYMONTHDAY":
                case "BYYEARDAY":
                case "BYWEEKNO":
                case "BYMONTH":
                case "BYSETPOS":
                case "BYHOUR":
                case "BYMINUTE":
                case "BYSECOND":
                    $params = explode(",", $param);
                    $this->{$rule}($params);
                    break;
            }
        }
        return $this;
    }