Thanks for the feedback guys! As a result I have done some benchmarking on the following:

• 200 iterations on opening a simple perl script - took 7 seconds (28.5/s)
• 5000 iterations on opening a socket inside a running perl script - took 10seconds (500/s)

So basically the overhead on just opening a perl script negates the use of trying to use shared memory to communicate between a persistent open socket script.

I will talk to the php developer and try to move forward with opening the socket directly from the php script. Even if the php script is forked off and each process has to open its own socket, it will still be faster

Thanks again for your feedback ikegami and browserUK