php calculate weeks between two dates

1//get Date diff as intervals 
2$d1 = new DateTime("2018-01-10 00:00:00");
3$d2 = new DateTime("2019-05-18 01:23:45");
4$interval = $d1->diff($d2);
5$diffInSeconds = $interval->s; //45
6$diffInMinutes = $interval->i; //23
7$diffInHours   = $interval->h; //8
8$diffInDays    = $interval->d; //21
9$diffInMonths  = $interval->m; //4
10$diffInYears   = $interval->y; //1
11
12//or get Date difference as total difference
13$d1 = strtotime("2018-01-10 00:00:00");
14$d2 = strtotime("2019-05-18 01:23:45");
15$totalSecondsDiff = abs($d1-$d2); //42600225
16$totalMinutesDiff = $totalSecondsDiff/60; //710003.75
17$totalHoursDiff   = $totalSecondsDiff/60/60;//11833.39
18$totalDaysDiff    = $totalSecondsDiff/60/60/24; //493.05
19$totalMonthsDiff  = $totalSecondsDiff/60/60/24/30; //16.43
20$totalYearsDiff   = $totalSecondsDiff/60/60/24/365; //1.35

1$startDate = new DateTime("2019-10-27");
2$endDate = new DateTime("2020-04-11");
3
4$difference = $endDate->diff($startDate);
5echo $difference->format("%a");

1function numWeeks($dateOne, $dateTwo){
2    //Create a DateTime object for the first date.
3    $firstDate = new DateTime($dateOne);
4    //Create a DateTime object for the second date.
5    $secondDate = new DateTime($dateTwo);
6    //Get the difference between the two dates in days.
7    $differenceInDays = $firstDate->diff($secondDate)->days;
8    //Divide the days by 7
9    $differenceInWeeks = $differenceInDays / 7;
10    //Round down with floor and return the difference in weeks.
11    return floor($differenceInWeeks);
12}
13
14$numOfWeek = numWeeks('2021-01-21', '2021-01-28');

1You are given two string (dd-mm-yyyy) representing two date, 
2you have to find number of all weekdays present in between given dates.
3  
4function number_of_days($days, $start, $end) {
5	$start = strtotime($start); $end = strtotime($end);
6	$w = array(date('w', $start), date('w', $end));
7	$x = floor(($end-$start)/604800);
8	$sum = 0;
9	for ($day = 0;$day < 7;++$day) {
10		if ($days & pow(2, $day)) {
11			$sum += $x + ($w[0] > $w[1]?$w[0] <= $day || $day <= $w[1] : $w[0] <= $day && $day <= $w[1]);
12		}
13	}
14	return $sum;
15}
16
17function getWeeklyDayNumbers($startDate, $endDate) {
18	$weekdays = array('monday' => 0, 'tuesday' => 0, 'wednesday' => 0, 'thursday' => 0, 'friday' => 0, 'saturday' => 0, 'sunday' => 0);
19	$weekdays['monday'] += number_of_days(0x02, $startDate, $endDate); // MONDAY
20	$weekdays['tuesday'] += number_of_days(0x04, $startDate, $endDate); // TUESDAY
21	$weekdays['wednesday'] += number_of_days(0x08, $startDate, $endDate); // WEDNESDAY
22	$weekdays['thursday'] += number_of_days(0x10, $startDate, $endDate); // THURSDAY
23	$weekdays['friday'] += number_of_days(0x20, $startDate, $endDate); // FRIDAY
24	$weekdays['saturday'] += number_of_days(0x40, $startDate, $endDate); // SATURDAY
25	$weekdays['sunday'] += number_of_days(0x01, $startDate, $endDate); // SUNDAY
26	return $weekdays;
27}
28
29$weekdays = getWeeklyDayNumbers('01-01-2021', '31-01-2021');
30print_r($weekdays);exit;
31