PHP - Php Threads

Hi

I wonder if anyone will be kind enough to help.

I am getting into forking with pcntl_fork()

I intend to create a script that runs 24/7 running 100 forks/children/'threads' simultaneously.

Once a child has finished it's task and exited how can I start a new child to replace it?

I need some kind of infinite loop that can continually check for exited children and set up new ones.  I'm finding it hard to get my head round since I'm new to forking.  Can anyone suggest a way to do this?

Thanks in advance.