Display sum of timestamps as 00:01:26 instead of 126 - php

Question

I'm working on a site where workers' hours are calculated based on when they clock in (start) and clock out (end). end - start = total. I have successfully computed the difference between the start and end. The start, end, and total are inserted into a DB. The "Shift total" comes from the SQL SUM of total in the db. The last foreach statement is the code in question. I want to format the "Shift total" as 00:00:00 so that it would show as 00:01:26 instead of 126. I have tried ". $row['SUM(total)'] + '00:00:00' . " but it didn't work. Any suggestions on how I should go about this? Thanks in advance. I pasted the results first then the code.
____start____________end____________total
10:44:46 AM 10:44:49 AM 00:00:03
10:50:12 AM 10:50:14 AM 00:00:02
10:50:27 AM 10:50:32 AM 00:00:05
11:12:02 AM 11:13:18 AM 00:01:16
Shift total --> 126
$sql3 = "SELECT date, startTime, endTime, total FROM timeSheet WHERE userName='$user_name'";
$sql4 = "SELECT SUM(total) FROM timeSheet WHERE userName='$user_name'";
echo "<table border='1'>
<tr>
<th>date</th>
<th>start</th>
<th>end</th>
<th>total</th>
</tr>";
foreach ($conn->query($sql3) as $row) {
$start = explode (" ", $row['startTime']);
$end = explode(" ", $row['endTime']);
if ($start[1] == '00:00:00'){
$start[1] = '0';
}else if ($end[1] == '00:00:00'){
$end[1] = '0';
}else{
$start[1] = date("h:i:s A", strtotime($start[1]));
$end[1] = date("h:i:s A", strtotime($end[1]));
}
echo "<tr>
<th>" . $row['date'] . "</th>
<th>" . $start[1] . "</th>
<th>" . $end[1] . "</th>
<th>" . $row['total'] . "</th>
</tr>";
}
foreach ($conn->query($sql4) as $row) {
echo "<tr>
<th></th>
<th></th>
<th>SUM</th>
<th>". $row['SUM(total)'] . "</th>
</tr>";
}
echo "</table>";

Answer 1

you can do it with the TIME function:
$sql4 = "SELECT TIME(SUM(total)) AS totalSum FROM timeSheet WHERE userName='$user_name'";
//....
foreach ($conn->query($sql4) as $row) {
echo "<tr>
<th></th>
<th></th>
<th>SUM</th>
<th>". $row['totalSum'] . "</th>
</tr>";
}
hint:
actually you don't need the total column in your database. You can use i.e
SELECT date, startTime, endTime, TIMEDIFF(startTime, endTime) AS total FROM timeSheet WHERE userName='$user_name'"
and
SELECT TIME(SUM(TIMEDIFF(startTime, endTime))) AS totalSum FROM timeSheet WHERE userName='$user_name'
for further information have a look at: http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_timediff