使用日期时间获取上周的最后一天

Question

I have tried the following code to get the last day of week in the next month:

$paymentMonth = "2017-07";
$wee = new \DateTime($paymentMonth);
$firstDate = clone $wee->modify(('Sunday' == $wee->format('l')) ? 'Monday last week' : 'Monday this week'); //Monday of last week of previous month

$lastDate = clone $wee->modify('+1 month')->modify(('Sunday' == $wee->format('l')) ? 'Sunday last week' : 'Sunday this week');
/**^^^^
  * This works in most cases of months
  * but for july 2017, I want the last day of the first week of next month.
  */

echo $firstDate->format('Y-m-d'); //Gives 26-june
echo $lastDate->format('Y-m-d'); //Gives 30-july in this case i want the 31 of july...

What is the cleanest way to get the last day of first week of next month using DateTime

Answer 1

Use format placeholder 'w' to obtain day of week of first of the month. Then subtract the relative number of the day you want to obtain (Sunday = 7, Saturday = 6, Friday = 5 and so on). If you want to obtain first Sunday of the month:

$paymentMonth = '2017-06-01';
$d = new DateTime($paymentMonth);
$w = $d->modify('+1 month')->format('w'); // * Returns 6 as 1st July 2017 is Saturday
$sun = (7-$w + 1)%7; // * First Sunday is 7-$w + 1 = 2
$lastDate = new DateTime($d->format('Y-m') . "-$sun");

Module %7 is required as on Sunday format('w') returns 0.

Don't rely on format('l') as result is environment dependent.

Answer 2

I found the solution, was pretty easy actualy :

$paymentMonth = '2017-07';
$fweek = new \DateTime($paymentMonth);
$firstDate = $fweek->modify(('Sunday' == $fweek->format('l')) ? 'Monday last week' : 'Monday this week'); //Monday of last week of previous month
$lweek = new \DateTime($paymentMonth);
$lastDate = $lweek->modify('+1 month')->modify(('Sunday' == $lweek->format('l')) ? 'Sunday last week' : 'Sunday this week'); //Sunday of first week of next month

echo $firstDate->format('Y-m-d') . ' - ' . $lastDate->format('Y-m-d');