Now this is an usefull and simple command, have you ever had a situation where you are programming socket daemons, or just any process in itself that could create several uncontrolled childs ?

Obviously killing the whole shell would fix the problem, but that quite savage , lets say you have several php childs running on the background and you want to kill them without killing php.

The following command will do the job:    kill -9 'pidof php'

Notice:

                        The "-9" option is the most severe kill option available