Calculates the end time given a start time a number of hours remaining

getEndTime.php

function getEndTime(DateTime $startDate, int $hoursRemaining) {
    $endDate = $startDate;

    # Can we finish it today?
    
    $hoursLeftInWorkday = $this->getHoursLeftInWorkday($startDate);
    
    if ($hoursRemaining < $hoursLeftInWorkday) {
        $endDate->modify('+' . $hoursRemaining . ' hours');
        return $endDate;
    }

    # How many full days after the rest of today are needed?

    $hoursRemainingAdjusted = $hoursRemaining - $hoursLeftInWorkday;
    $endDate = $endDate->modify('+1 day');

    # Can we finish on the current $endDate?
    while ($hoursRemainingAdjusted - 8 >= 0 ) {

        # skip the weekends
        while ($endDate != WORKDAY) {
            $endDate->modify('+1 day');
        }

        # use up a workday
        $hoursRemainingAdjusted = $hoursRemainingAdjusted - 8;
        $endDate->modify('+1 day');
    }

    # How many partial day hours are needed after that

    $endDateHour = WORKDAY_START_HOUR + $hoursRemainingAdjusted;
    $endDate = $endDate->setTime($endDateHour, 00)

    return $endDate;
}