Difference among sleep() and usleep() in PHP

Question

Can any body explain me what is the difference among sleep() and usleep() in PHP.

I have directed to use following scripts to do chat appli

Answer 1

sleep() allows your code to sleep in seconds.

• sleep(5); // sleeps for 5 seconds

usleep() allows your code with respect to microseconds.

• usleep(2500000); // sleeps for 2.5 seconds