2^nd and 4^th Saturday of the month

$year=date('Y');  // Change the value to use different Year
$month=date('m'); // Change the value to use different month
//$month=9;
$firstday = new  DateTime("$year-$month-1 0:0:0");
$first_w=$firstday->format('w'); // weekday of firstday 
$saturday1=new DateTime;
$saturday1->setDate($year,$month,14-$first_w);
echo "2nd Saturday for the Month:
	$month of Year:$year :".$saturday1->format('d-m-Y');

$saturday2=new DateTime;
$saturday2->setDate($year,$month,28-$first_w);
echo "4th Saturday for the Month:
	$month of Year:$year :".$saturday2->format('d-m-Y')";

$monday1=new DateTime;
$monday1->setDate($year,$month,2-$first_w);
echo "1st monday for the Month:
		$month of Year:$year :".$monday1->format('d-m-Y'); 

$wednesday3=new DateTime;
$wednesday3->setDate($year,$month,18-$first_w);
echo "3rd wednesday for the Month:
		$month of Year:$year :".$wednesday3->format('d-m-Y');	

Formula for any day any week

my_number=day_number + (Week_number-1)*7

my_number=4 + (3-1);
$wednesday3->setDate($year,$month,my_number-$first_w);