อยากทราบวิธีหาว่าอยู่สัปดาห์ที่เท่าไหร่ โดยกำหนดวันเริ่มต้นและวันที่ เองอ่าครับ

echo $week = date("W", strtotime('2014-03-28')); //13

function numWeek($strStartDate,$strEndDate){//2012-02-01

	$intMonday = 0;
	$intOther = 0;
	$intRound = array();
	$i = 0;

	while (strtotime($strStartDate) <= strtotime($strEndDate)) {
		$DayOfWeek = date("w", strtotime($strStartDate));
		if($DayOfWeek == 1)  // 1 = monday
		{
			$intMonday++;
			$intOther = 0;
			$intRound[$i] = 1;
		}else{
			$intOther++;
		}

		$strStartDate = date ("Y-m-d", strtotime("+1 day", strtotime($strStartDate)));
	}
	if($intOther > "0" && $intRound[0] =! "1"){
		$intMonday++;
	}
	$i++;
	return $intMonday;
}

echo $week = date("W", strtotime('2014-03-28')); //13

SET DATEFIRST 7 -- Sunday
SELECT @@DATEFIRST

SET DATEFIRST 1 -- Monday

DECLARE @startDate DATE = '2014-01-01', @endDate DATE = '2014-12-31';

--CROSS JOIN
;WITH t1(N) AS (SELECT N FROM (VALUES(1),(1)) TableValueExpression(N)), -- 2 Rows
      t2(N) AS (SELECT 1 FROM t1 x, t1 y), -- 4 Rows (2*2)
      t3(N) AS (SELECT 1 FROM t2 x, t2 y), -- 16 Rows (4*4)
      t4(N) AS (SELECT 1 FROM t3 x, t3 y), -- 256 Rows (16*16)
      t5(N) AS (SELECT 1 FROM t4 x, t4 y), -- 65,536 Rows (256*256)
      tally(N) AS (SELECT 0 UNION ALL
                  SELECT TOP (DATEDIFF(WEEK, @startDate, @endDate)) -- Limit the result-set straight up front
                  ROW_NUMBER() OVER(ORDER BY (SELECT NULL))
                  FROM t5 x, t5 y) -- 4,294,967,296 Rows (65,536*65,536)
SELECT N + 1  AS WeekNo,
CASE WHEN DATEADD(WEEK, DATEDIFF(WEEK, '1900-01-02', DATEADD(WEEK, N, @startDate)), '1900-01-02') < @startDate 
     THEN @startDate
     ELSE DATEADD(WEEK, DATEDIFF(WEEK, '1900-01-02', DATEADD(WEEK,N , @startDate)), '1900-01-02') END AS weekStart,
CASE WHEN DATEADD(WEEK, DATEDIFF(WEEK, '1900-01-08', DATEADD(WEEK, N + 1, @startDate)), '1900-01-08') > @endDate 
     THEN @endDate
     ELSE DATEADD(WEEK, DATEDIFF(WEEK, '1900-01-08', DATEADD(WEEK, N + 1, @startDate)), '1900-01-08') END AS weekEnd
FROM tally;

$start = new DateTime('2014-03-01');
$end = new DateTime('2014-04-06');

$week = intval($end->format('W')) - intval($start->format('W'));