While using nginx and trying to follow the instructions to fix post_max_size PHP parameter (which should be < 32M in order for this issue to appear), the instructions will say that only restarting the webserver is enough, but actually after editing the file, the issue is still not gone because, while using NGINX, you need to do (in debian) service php5-fpm reload.
It would be nice to include that command in the instructions so people don't get confused as only restarting the web server won't fix the issue.