How do I play an audio file at the end of a countdown using PHP?

I am developing a little tool for myself that keeps track of all the steps for a project as well as the time it takes me to do each step. I also want to be set it up so that for example after 30 minutes of working on a tough project, an audio file plays that says "Take a break. You earned it." and then after another 10 minutes, another audio file plays that says "Time to get back to work." How do I use PHP to play an audio file at the end of a countdown?