php behavior when post_max_size exceeded

Question

I understand that if a POST request exceeds post_max_size, the $_POST and $_FILES superglobals become empty.

I've seen plenty of discussions about how to detect this scenario, but never an explanation of why the superglobals are empty. It seems really odd to me to wipe out the POST data, forcing the user to reenter their answers. Is it a security precaution perhaps?

Curious about other languages (java, .net). Do they behave similarly?

Thanks

Answer 1

If an array can only fit 50 indexes and you push 100, would you expect the other 50 to remain somewhere?

The same applies to this setting. Though there may be SOME POST data that can fit in the maximum size, having a piece of the expected whole would cause far more problems than having none at all. Right?

It's far easier to detect an EMPTY post than it is to detect an incomplete one.

I believe this is their rationale.

Answer 2

To answer part of your second question, with .NET, if the POST is larger than maxRequestLength (part of the .NET configuration), but smaller than maxAllowedContentLength(part of the IIS configuration) you can create a custom HTTP module to get at the portion of the POST that came through.

Without the custom HTTP module, it'll just throw an exception. And you want maxRequestLength to be the limiting factor, otherwise IIS will deal with it instead of .NET.