Note that if you need to be "interactive" with the user *and* the opened application, you can use stream_select to see if something is waiting on the other side of the pipe.
Stream functions can be used on pipes like :
- pipes from popen, proc_open
- pipes from fopen('php://stdin') (or stdout)
- sockets (unix or tcp/udp)
- many other things probably but the most important is here
More informations about streams (you'll find many useful functions there) :
http://www.php.net/manual/en/ref.stream.php