title: How to get time difference between two time in a same days?
body: <p>I'm new to CodeIgniter &amp; PHP.<br>
  In my database I store users status in IN time and Out Time. I want to calculate that time means, how much time a user was logged in on a particular day. The user may be logged in more than one time or logged out on a particular day.<br>
  How can I calculate the time?</p>
  
  <p>Time format is=04:06:37.
  If the user logged in 04:06:37 and logged out 04:09:37, then the time difference is 3 min and 0 sec.</p>