The first script, prefork.php, is for forking a given function from a given file and running n children that will execute that function. There can be a startup function that is run before any forking begins and a shutdown function to run when all the children have died.
The second script, prefork_class.php, uses a class with defined methods instead of relying on the command line for function names. This script has the added benefit of having functions that can be run just before each fork and after each fork. This allows the parent process to farm work out to each child by changing the variables that will be present when the child starts up. This is the script we use for managing our Gearman workers. We have a class that controls how many workers are started and what functions they provide. I may release a generic class that does that soon. Right now it is tied to our code library structure pretty tightly.
We have also included two examples. They are simple, but do work to show you how the scripts work.