date() : First monday of first week of month? - php

Question

I am actually trying to make a monthly reward system with a "stamp" interface.
For that, I want to use an HTML Table with 1 cell = 1 day, starting Monday.
Here is my problem (and the solution is probably easy to find !) : Monday isn't the first day of month - not for all month, atleast. How can I ask strtotime() & date() to show the date Y-m-d for :
"monday of first week of month" ?
"sunday of last week of month" ?
I'm expecting result like this for 2019-08 :
2019-07-29
2019-09-01
I did not find it on PHP Documentation but is there a way to place a third argument on date() to set up the date ?
Like that, I could have done something like this :
date('Y-m-d', strtotime('monday'), '2019-08-01');
EDIT :
Based on #Vidal answer here is what I tried, but I got a strange PHP reaction :
$first_date = date("Y-m-d", strtotime("first monday 2019-08 - 7 days"));
$last_date = date("Y-m-d", strtotime("last sunday 2019-09"));
$last_date2 = date("Y-m-d", strtotime("last sunday 2019-09 + 7 days"));
echo $first_date; ?><br>
echo $last_date; ?><br>
echo $last_date2; ?><br>
Output :
2019-07-29
2019-08-25
2019-09-08
I don't know why. Did you also notice that I need to set $last_date & $last_date2 to 2019-09 instead of 2019-08 ?

Answer 1

I think it's better to work with the DateTime object.
/*
I'm expecting result like this for 2019-08 :
"monday of first week of month" => 2019-07-29
"sunday of last week of month" => 2019-09-01
*/
$month = "2019-08";
$date = date_create($month."-02")
->modify("last Monday")
->format('l, d-m-Y')
;
echo $date."<br>";
$date = date_create("last Day of ".$month)
->modify("-1 Day")
->modify("next Sunday")
->format('l, d-m-Y')
;
echo $date."<br>";
/* Output
Monday, 29-07-2019
Sunday, 01-09-2019
*/

Answer 2

Do a loop for year, month.
echo date("j, d-M-Y", strtotime("first monday of 2019-08"));
echo date("j, d-M-Y", strtotime("last sunday of 2019-08"));
Hope it helps.
PHP Reference

Answer 3

I managed to make it work by changing some things to your code:
1) If the first monday is > 2 and <= 7, you have to remove 7 days to actually get the first monday
2) I added the '+ 7 days' on another line of code. It didn't work if I had 'last sunday of XXXX-XX + 7 days'
3) To get the last sunday based on your desired outputs, I compared the last sunday of the month with the total number of days in the month - 7. If it's bigger than that (25 for example), it means that it's not the last sunday
$year = 2019;
$month = 8;
if($month < 10)
$month = "0" . $month;
$currentDate = $year . "-" . $month;
if(date("d", strtotime("first monday of " . $currentDate)) > 2 && date("d", strtotime("first monday of " . $currentDate)) <= 7)
$first_date = date("Y-m-d", strtotime("first monday of " . $currentDate . " -7 days"));
else
$first_date = date("Y-m-d", strtotime("first monday of " . $currentDate));
if(date("d",strtotime("last sunday of " . $currentDate)) > date('t') - 7)
{
$last_date = date("Y-m-d", strtotime("last sunday of " . $currentDate));
$last_date = date("Y-m-d",strtotime($last_date . " +7 days")); //working when you add days like that. doesn't work if I put + 7 days in the 'last sunday of'...
}
else
$last_date = date("Y-m-d", strtotime("last sunday of " . $currentDate));
echo $first_date . "<br>";
echo $last_date . "<br>";