Since PHP is designed to be run on many platforms, and process-killing is a very OS-specific function, PHP doesn't provide this capability. However, if you can find (or create) a program which can be made to kill another process via the command line (in Linux, this is trivial, but I don't belive Windows comes with any such functionality), you can use the program execution functions
to issue the kill command. A brief search found this page
, which has a few tools which might come in handy. Otherwise, a good Googling should get you what you're after.