date_default_timezone_set("Europe/Rome");
$today = new DateTime();
$numDay = date("w");
//echo "<br>today = ".$today->format('Y-m-d H:i:s');

switch($numDay){
    //monday
    case 1 :
        $startWeek = $today->format('Y-m-d 00:00:00');
        $endWeek = $today->modify('next sunday')->format('Y-m-d 23:59:59');
    break;
    /*//sunday
    case 0 :
        $startWeek = $today->modify('last monday')->format('Y-m-d 00:00:00');
        $endWeek = $today->format('Y-m-d 23:59:59');
    break;*/
    default:
        $startWeek = $today->modify('last monday')->format('Y-m-d 00:00:00');
        $endWeek = $today->modify('next sunday')->format('Y-m-d 23:59:59');
    break;
}

//echo "<br><br>start week = ".$startWeek;
//echo "<br>end week = ".$endWeek;

$startMonth = $today->modify('first day of this month')->format('Y-m-d H:i:s');
$endMonth = $today->modify('last day of this month')->format('Y-m-d 23:59:59');

//echo "<br><br>start month = ".$startMonth;
//echo "<br>end month = ".$endMonth;