Root path for 404 PHP page under nginx (php-fpm) doesn't work

Question

If I try to access anything unexisting in the site's root directory, ie http://example.com/unexisting.php , I get right good answer from my custom 404 page using the following config:

server_name example.com;
root        /path/to/example;
index       index.php;
error_page 404  /not_found.php;

location ~ index\.php
{
    try_files $uri/index.php =404;
    return 301 $scheme://$server_name/;
}

location ~ not_found\.php
{
    root        /path/to/example;
    allow all;
    internal;
    fastcgi_intercept_errors off;
    fastcgi_param SCRIPT_FILENAME $document_root/not_found.php;
    include fastcgi_params;
}

location = /
{
    try_files $uri/index.php @static;
    fastcgi_split_path_info ^(.+\.php)(/.+)$;
    fastcgi_param SCRIPT_FILENAME $document_root/index.php;
    include fastcgi_params;
}

location ~ \.php$
{
    try_files $uri $uri/ =404;
    fastcgi_split_path_info ^(.+\.php)(/.+)$;
    fastcgi_intercept_errors on;
    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    include fastcgi_params;
}

location @static
{
    try_files $uri $uri/ =404;
    expires max;
}

location /
{
    try_files /something_non_existing @static;
}

If I try to access files out the root folder, ie " http://example.com/unexisting_dir/unexisting.php ", the 404 page is on the screen, but without any graphics. Because in logs are things like "GET /unexisting_dir/images/some_image_for_404_page.png HTTP/1.1" and nginx returns nothing, 'cause it has a wrong base from the user request. Meanwhile, I've checked that $document_root has the right base, so php-fpm works perfect.

The question is how to make nginx ignore user's URI in case of servicing 404 page for unexisting nested (embedded) directories (without redirecting and harming anything potential) ?

Many thanks in advance!

This is "fastcgi_params" (just in case):

    fastcgi_param  QUERY_STRING       $query_string;
    fastcgi_param  REQUEST_METHOD     $request_method;
    fastcgi_param  CONTENT_TYPE       $content_type;
    fastcgi_param  CONTENT_LENGTH     $content_length;
    fastcgi_param  SCRIPT_NAME        $fastcgi_script_name;
    fastcgi_param  REQUEST_URI        $request_uri;
    fastcgi_param  DOCUMENT_URI       $document_uri;
    fastcgi_param  DOCUMENT_ROOT      $document_root;
    fastcgi_param  SERVER_PROTOCOL    $server_protocol;
    fastcgi_param  HTTPS              $https if_not_empty;
    fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
    fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;
    fastcgi_param  REMOTE_ADDR        $remote_addr;
    fastcgi_param  REMOTE_PORT        $remote_port;
    fastcgi_param  SERVER_ADDR        $server_addr;
    fastcgi_param  SERVER_PORT        $server_port;
    fastcgi_param  SERVER_NAME        $server_name;
    fastcgi_param  REDIRECT_STATUS    200;
    fastcgi_pass unix:/var/run/php5-fpm.sock;

Answer 1

The issue here is not nginx. It is correctly returning the output of not_found.php

You need to ensure that the output includes absolute paths to your images instead of relative in the HTML. Eg

<img src="/notfound.jpg" />

Instead of

<img src="notfound.jpg" />

The extra forward slash tells the browser to request the images from the document root instead of the current "directory" that the browser has requested.