Very strange form behaviour

I can't work this out. One minute it was working fine and now it's not and I can't see what's changed!! My problem is simply submitting a username and password for a login function. The form method is set to "post" but for 开发者_如何学Gosome reason no data is getting through. If I dump $_REQUEST or $_POST they return empty. I know the form is submitting because if I change the method to "get" I receive the data as expected. Can anyone think of any reason why "get" would work when "post" isn't?!?!? If it's relevant, I'm using the codeigniter framework.

I would check first whether this hasn't got any CI specific reasons as @Pete points out.

The only other idea that comes to mind is that maybe you have a .htaccess file with mod_rewrite directives somewhere, and that a header redirect is done for some reason rather than an internal one. A header redirect would pass along GET variables (if using [QSA]) but lose POST ones.

I seem to remember that codeignitor prevents direct access to $_POST - check the docs (some thing like $this->input->post or similar)