public static function toString($dayOfWeek)
    {
        return isset(self::$strings[$dayOfWeek]) ? self::$strings[$dayOfWeek] : null;
    }
public static function toString($dayOfWeek)
    {
        return isset(self::$strings[$dayOfWeek]) ? self::$strings[$dayOfWeek] : null;
    }
public static function toString ( $ dayOfWeek ) { return isset ( self :: $ strings [ $ dayOfWeek ] ) ? self :: $ strings [ $ dayOfWeek ] : null ; }
Returns a string representation of a day.

@param int $dayOfWeek

@return string|null
Returns a string representation of a day .