Q:

How to convert seconds to time format?

For some reason I convert a time format like: 03:30 to seconds 3*3600 + 30*60, now. I wanna convert it back to its first (same) format up there. How could that be?
My attempt:
3*3600 + 30*60 = 12600 

12600 / 60 = 210 / 60 = 3.5, floor(3.5) = 3 = hour

Now, what about the minutes? 
Considering the value can be like 19:00 or 02:51. 
I think you got the picture.
And by the way, how to convert 2:0 for example to 02:00 using RegEx?

A:

This might be simpler
gmdate("H:i:s", $seconds)
PHP gmdate

A:

$hours = floor($seconds / 3600);
$mins = floor($seconds / 60 % 60);
$secs = floor($seconds % 60);

If you want to get time format:
$timeFormat = sprintf('%02d:%02d:%02d', $hours, $mins, $secs);

A:

If the you know the times will be less than an hour, you could just use the date() or $date->format() functions.
$minsandsecs = date('i:s',$numberofsecs);

This works because the system epoch time begins at midnight (on 1 Jan 1970, but that's not important for you).
If it's an hour or more but less than a day, you could output it in hours:mins:secs format with `
$hoursminsandsecs = date('H:i:s',$numberofsecs);

For more than a day, you'll need to use modulus to calculate the number of days, as this is where the start date of the epoch would become relevant.
Hope that helps.

