Get finish date, given start date and schedule in week - php

Question

I have a problem using PHP to get the finish date of course, as below:
Inputs:
Start date (e.g: 8/23/2019)
Schedule in week (e.g: Monday, Tuesday, Friday)
Total of lessons (e.g: 8)
Output: The finish date of course (is 9/9/2019 with above e.g inputs).
One lesson is one day. Input fields from end user:
Sorry for my bad English. Thank you very much!

Answer 1

As I see it loop while there are lessons left and subtract when it's Monday, Tuesday or Friday.
After the loop output the date.
$start = "8/23/2019";
$days = ["Monday", "Tuesday", "Friday"];
$n = 8;
$d = strtotime($start);
while($n>0){
//See if day is in days array
if(in_array(date("l", $d), $days)){
$n--;
}
$d += 86400; // go to next day
}
echo date("m/d/Y", $d-86400); //-86400 because the loop adds one at the end.

Answer 2

Try this code, if I understand you correctly))
<?
$startDay = '2019-09-25';
$aSchedule = array(1,2,4);
$iCntShed = count($aSchedule);
$iLessonsCnt = 8;
$iDWStartDay = date('w',strtotime($startDay));
$aDOWMap = array('Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat');
// first day according Schedule array and startDay
$aWeekDays = array_filter($aSchedule,function($iSDW) use ($iDWStartDay){
return $iSDW>= $iDWStartDay;
});
// day according of week
$nextDate = date('Y-m-d',strtotime($startDay.' next '.$aDOWMap[end($aWeekDays)]));
$i = 0;
while (count($aWeekDays)<$iLessonsCnt) {
$i = $i<$iCntShed ? $i : 0;
$aWeekDays[] = $aSchedule[$i];
$nextDate = date('Y-m-d',strtotime($nextDate.' next '.$aDOWMap[$aSchedule[$i++]]));
}
print_r($aWeekDays);
echo $nextDate;