fork-helper | A PHP helper to fork processes and allow multi-threading | Architecture library

The linked library seems to be internally using pcntl_fork which performs a true fork of the running PHP process. The library mentions "threading" but this is not correct. Forking is a pretty low level operating system concept whereas a process creates a copy of its memory space and instructions in a new process. That new process becomes a child process of the forking process.

This means that everything, like included code and instantiated objects are copied and therefore a child process cannot directly modify the objects of the parent process. The only ways a child process can communicate with the parent is shared memory. In addition the parent can "wait" for the child process to terminate (failing to do this may result in zombie child processes). The linked library does not seem to implement true shared memory but (if you must) you could probably use the PHP shared memory library.

This however is impractical for simple tasks like the one you're sharing. In your case you need to use a true threading library like e.g. pthreads. Threads, unlike processes, are part of the parent process and share the same memory and data structures and have a significantly lower overhead when context switching.

Note: All the above concepts are pretty low level ones so maybe PHP is not the best choice of language to implement these.