NGINX - rewrite and error 404 - nginx

Question

my rewrite works.
On the other hand my 404 error redirection does not work anymore.
If I add to my .php link it returns me there is no file.
Similarly when I put in my link an admin / it puts me the opening, the menu and the copiryght.
Example if I put https://mon.domain.com/admin/ it loads me a page while I would like my 404 error page.
What I would like, if the pages does not exist that in any case I come across my error 404
Can you help me?
Here is the configuration of nginx:
upstream www {
server unix:/var/run/php5-fpm.sock;
}
server {
listen 80 default;
server_name no-impact.eu;
return 301 https://my.domain.com;
}
server {
listen 443 ssl;
server_name my.domain.com;
fastcgi_param HTTPS on;
ssl on;
ssl_certificate /etc/letsencrypt/live/my.domain.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/my.domain.com/privkey.pem;
ssl_session_timeout 5m;
ssl_protocols SSLv2 SSLv3 TLSv1;
ssl_ciphers HIGH:!aNULL:!MD5;
ssl_prefer_server_ciphers on;
root /var/www/my.domain.com/;
index index.php;
error_page 400 401 402 403 404 500 502 503 504 /error.html;
location /.well-known/acme-challenge {
root /var/www/letsencrypt;
}
location = /error.html {
root /var/www/my.domain.com/error/;
index index.html;
}
location / {
index index.php index.html;
try_files $uri $uri/ #rewrite;
}
location #rewrite {
rewrite ^/([\w-]+)-page-(\d+)$ /index.php?id=$1&page=$2 last;
rewrite ^/([\w-]+)-(\d+)$ /index.php?id=$1&id_tutoriel=$2 last;
rewrite ^/(.*)$ /index.php?id=$1 last;
}
location ~ \.php$ {
try_files $uri =404;
fastcgi_split_path_info ^(.+\.php)(/.+)$;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
include fastcgi_params;
}
}

Answer 1

The problem here is that your rewrite tells nginx to redirect everything to the backend, so nginx does not detect a 404 by itself. Your backend then handles the request and sends a 404, which nginx sends back directly to the client.
In order for nginx to intercept the 404 and show its own error page, you need to add the directive fastcgi_intercept_errors on; to your .php-location.