How to create a timer

Question

Using mysqli the $dbSessionDuration variable can bind the result of data from the query into this variable.  The $dbSessionDuration variable holds time so the variable has a time format as below:

01:30:10

I want to display $dbSessionDuration value in a timer so that in the above's example it will start ticking down from 01:30:10 and go all the way to 0 when it stops.  Can someone tell me how I can create a timer and place whatever value $dbSessionDuration value in the timer to count down to 00:00:00?