PHP time add HH:MM:SS - php

Question

I am trying to add total worked hrs for the employees for the 7 days week period below code is not working for me, not sure what am i doing wrong as I am not a PHP expert, idea please?
<?php
$time1 = $row_Roster['sunday_start'];
$time2 = $row_Roster['sunday_end'];
list($hours, $minutes, $seconds) = explode(':', $time1);
$startTimestamp = mktime($hours, $minutes, $seconds);
list($hours, $minutes, $seconds) = explode(':', $time2);
$endTimestamp = mktime($hours, $minutes, $seconds);
$add = $endTimestamp - $startTimestamp;
if($seconds < 0) {
$seconds+=60*60*24;
}
$seconds = $add % 60;
$minutes = ($add / 60) % 60;
$hours = floor($add / (60 * 60));
$sunday = sprintf('%02d:%02d:%02d', $hours, $minutes, $seconds);
echo $sunday;
if ($sunday >8)
echo ('</br><span class="smallred">Long Shift</span>');
?>
does it make sense
list($hours, $minutes, $seconds) = explode(':', $time1);
$Timestamp1 = mktime($hours, $minutes, $seconds);
list($hours, $minutes, $seconds) = explode(':', $time2);
$Timestamp2 = mktime($hours, $minutes, $seconds);
list($hours, $minutes, $seconds) = explode(':', $time3);
$Timestamp3 = mktime($hours, $minutes, $seconds);
list($hours, $minutes, $seconds) = explode(':', $time4);
$Timestamp4 = mktime($hours, $minutes, $seconds);
$add = $Timestamp1 + $Timestamp2 + $Timestamp3 + $Timestamp4;
if($seconds < 0) {
$seconds+=60*60*24;
}
$seconds = $add % 60;
$minutes = ($add / 60) % 60;
$hours = floor($add / (60 * 60));
$total = sprintf('%02d:%02d:%02d', $hours, $minutes, $seconds);
echo $total;
?>

Answer 1

You make this way to complicated.
First just put all your formatted days into an array ($formattedWorkTimeWeekdays).
Then go through each day with array_map() and calculate the total amount of seconds per day and save it in $secondsWorkTimeWeekdays.
After this you can sum all seconds per day together with array_sum() and you get the total amount of work for this week in seconds in the variable $totalSecondsWorkTimeWeek.
And at the end simply calculate the hours, minutes and seconds out of it.
<?php
$formattedWorkTimeWeekdays = [
$monday,
$tuesday,
$wednesday,
$thursday,
$friday,
$saturday,
$sunday,
];
$secondsWorkTimeWeekdays = array_map(function($formattedWorkTimeDay){
list($hours, $minutes, $seconds) = explode(":", $formattedWorkTimeDay);
return ($hours * 3600) + ($minutes * 60) + $seconds;
}, $formattedWorkTimeWeekdays);
$totalSecondsWorkTimeWeek = array_sum($secondsWorkTimeWeekdays);
$hoursWorkTimeWeek = $totalSecondsWorkTimeWeek / 3600;
$minutesWorkTimeWeek = ($totalSecondsWorkTimeWeek % 3600) / 60;
$secondsWorkTimeWeek = ($totalSecondsWorkTimeWeek % 3600 % 60);
echo $total = sprintf('%02d:%02d:%02d', $hoursWorkTimeWeek, $minutesWorkTimeWeek, $secondsWorkTimeWeek);
?>
EDIT:
After your edit your have 2 completely different codes, which aren't related to each other at all. For your first revision I gave the answer above.
Now in your edited code you just seem to have 2 dates. You can just create two DateTime objects and get the difference from them, e.g.
$workTimeStart = new DateTime($row_Roster['sunday_start']);
$workTimeEnd = new DateTime($row_Roster['sunday_end']);
$workTimeDifference = $workTimeStart->diff($workTimeEnd);
echo $workTimeDifference->format("%h hours %i minutes %s seconds");

Answer 2

Instead of calculations and calling sprintf, you can use gmdate function:
//the same code summing the weekdays seconds
$add = $Timestamp1 + $Timestamp2 + $Timestamp3 + $Timestamp4;
print gmdate("H:i:s", $add);