private function getDay($dayNumber)
    {
        return isset($this->days[$dayNumber]) ? $this->days[$dayNumber] : null;
    }
private function getDay($dayNumber)
    {
        return isset($this->days[$dayNumber]) ? $this->days[$dayNumber] : null;
    }
private function getDay ( $ dayNumber ) { return isset ( $ this -> days [ $ dayNumber ] ) ? $ this -> days [ $ dayNumber ] : null ; }
Gets the day corresponding to the day number.

@param int $dayNumber

@return DayInterface|null
Gets the day corresponding to the day number .