calculate night hours between two date - php

Question

I want to calculate night hours (21PM to 6AM) between two given dates.
I don't have any ideas
public function biss_hours($start, $end){
$startDate = new \DateTime($start);
$endDate = new \DateTime($end);
$periodInterval = new \DateInterval( "PT1H" );
$period = new \DatePeriod( $startDate, $periodInterval, $endDate );
$count = 0;
foreach($period as $date){
$startofday = clone $date;
$startofday->setTime(5,59);
$endofday = clone $date;
$endofday->setTime(20,59);
if($date > $startofday && $date < $endofday){
$count++;
}
}
return $count;
}
I have this fonction but it's don't work :)
Thx any help

Answer 1

There is no need to loop over a period. As already suggested in the comments, start by calculating the hours of the start and end date since these are the ones that can actually contain less than a full nights hours. Once those are calculated, you can simply get the number of days remaining and multiply them by the amount of hours a night has.
Please note that I only consider hours in my example below, so 22:55 to 24:00 would result in 2 full hours of night time counted. Also it does not check cases where the end date is before the start date or whether inputs are valid. It should get the idea across though:
function getHoursForSingleDay ( $startTime, $endTime, $nightStart, $nightEnd ) {
$numHours = 0;
// if the day starts before night ends
if( $startTime < $nightEnd ) {
// e.g. Night ends at 6a.m. - day starts at 5 a.m. = 1 hour
$numHours += $nightEnd - $startTime;
}
// if the day ends after night starts
if( $endTime > $nightStart ) {
// e.g. day ends at 23 - night starts at 21 = 2 hours
$numHours += $endTime - $nightStart;
}
return $numHours;
}
function biss_hours ( $start, $end, $nightStart = 21, $nightEnd = 6 ) {
$startDate = new \DateTime( $start );
$endDate = new \DateTime( $end );
$startTime = intval( $startDate->format( 'H' ) );
$endTime = intval( $endDate->format( 'H' ) );
// Both dates being the same day is an edge case
if( $startDate->format( 'Y-m-d' ) === $endDate->format( 'Y-m-d' ) ) {
return getHoursForSingleDay( $startTime, $endTime, $nightStart, $nightEnd );
}
// get the hours for bot the start and end date, since they can be less than a full night
$numHours = getHoursForSingleDay( $startTime, 24, $nightStart, $nightEnd );
$numHours += getHoursForSingleDay( 0, $endTime, $nightStart, $nightEnd );
// all remaining days in between can be calculated in a rather simple way
$nightHoursPerDay = $nightEnd + ( 24 - $nightStart );
// -1 because diff returns 1 for two adjacent days, but we treat the first and last day specially
$numDaysBetween = intval( $endDate->diff( $startDate )->format( "%a" ) ) - 1;
$numHours += $numDaysBetween * $nightHoursPerDay;
return $numHours;
}