Nginx 404 pages request method is always GET - nginx

Question

When I post to a 404 page, nginx is stripping the post data and changing the request method to "GET". How do I prevent this? I have nginx configured to serve a php file as the error 404 page that is in the root of the domain directory. I would like to keep a log of whatever is posted to it.
nginx.conf
server {
listen 80;
error_page 404 = /404.php;
set $oldhost $host;
root /var/www/www/$oldhost;
location ~* \.(?:ico|css|js|gif|jpg|png|html|htm)$ {
expires 3d;
add_header Pragma public;
add_header Cache-Control "public";
}
location = /favicon.ico {
log_not_found off;
access_log off;
}
location = /robots.txt {
allow all;
log_not_found off;
access_log off;
}
location / {
index index.php index.htm index.html;
try_files $uri $uri/ /index.php?$args;
}
location ~ .php$ {
location ~ \..*/.*\.php$ {return 404;}
expires 1d;
add_header Pragma public;
client_max_body_size 80m;
add_header Cache-Control "public";
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_buffers 16 16k;
fastcgi_buffer_size 32k;
fastcgi_intercept_errors on;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include fastcgi_params;
}
}

Answer 1

This happens because when nginx cannot find a page, it will redirect (GET) the user to that 404.php page you defined.
What you need to do is to add it to the try_files directive, so nginx will try to post to it when it cannot find the others, or make it that you can handle 404 error directly on your index.php (like wordpress does).
EDIT:
location / {
index index.php index.htm index.html;
try_files $uri $uri/ /index.php?$args 404.php 404.php?$args;
}