how to program "there are 12 users online" etc.?

check out this

how do they do the program to tell how many users online?

there is the same feature in the phpBB etc.

how do we do this in php? any information you think will be helpful, please help.

thanks.

Search the forums. Here's a hint of the sort of search string to use: users online.

Most of the code on my site is a very old, and I really should do some updating. But you can find what your looking for on there.