How can i sum multiple time in laravel 5.2

For example, I have multiple time like:

  $a = "9:00:00";
  $b = "8:00:00";
  $c = "9:00:00";

and so on...

It must return in 26:00:00 and how to subtract it from 45:00:00 ...

I have to find out total working hours and overtime for my attendance.

Please help.

via Chebli Mohamed