> Nothing at all to do with PHP.

I think you did not understand what I wrote.

The OP asked if one can spoof the IP address while requesting a document.
Jerry says (correctly) that it would not be possible to get the answer.
That might imply that is IS possible to make a request, but the answer
goes nowhere. That would be enough if the purpose of the request was
e.g. to delete a database by SQL injection. The answer is unimportant.

What I said was that I think it is not even possible to make a request
(regardless where the answer would go), because that would require a
connection which cannot be established with a spoofed IP.