Date-Time Counter in PHP
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I am developing a project using PHP in which I want to do something like this:

    -> User Enter Start and End date and time both. On this page user has Play/Pause button.
    -> User Enter details and save it to database. When user save this details counter will starts running. and using Play/Pause button user can pause and resume the counter. May be user pause counter today and resume it any time like after two days. 

So how can I maintain this counter timing.

Can any one help me through code or any guidance?

Thank You in Advance