Fork() in php?

What do you guys think about having fork, waitpid, and signal handling available in php? I wrote a few simple fork test functions, and everything seemed to work fine. I am thinking that with sockets, shm, signals, and fork capability, there could be the possibility of someone writing daemons in php : ) Can anyone think of possible problems that could occur in supporting this functionality? If it were to be added, where should it be added? IMO this type of thing probably shouldn't exist in ext/standard. Thanks, -Jason