process creation

A simple question (or so I thought). Does php allow an app to create/start a process/application that can continue to run on its own, after the initiating program/app terminates? It appears that the spawning/forking functions might work, but the child apps would be in a zombie status, and couldn't be killed by an external program. Basically, I'd like to create a bunch of test apps/processes, and then to be able to kill them by a separate process if the apps take too long to run.. So.. thoughts/comments would be appreciated! thanks