Symfony 4 how to enable prod mode?

You have to ensure that the environment variable APP_ENV is set correctly in your production environment. The documentation tells you how to do this for various web servers. For example, in your Apache-configuration you have to use SetEnv. This could look something like this:

DocumentRoot /var/www/project/public<Directory /var/www/project/public>    AllowOverride None    Order Allow,Deny    Allow from All    <IfModule mod_rewrite.c>        Options -MultiViews        RewriteEngine On        RewriteCond %{REQUEST_FILENAME} !-f        RewriteRule ^(.*)$ index.php [QSA,L]    </IfModule></Directory>SetEnv APP_ENV prodSetEnv APP_DEBUG 0...

A similar configuration for nginx would use fastcgi_param and would look somewhat like this:

location ~ ^/index\.php(/|$) {    fastcgi_pass unix:/var/run/php7.1-fpm.sock;    fastcgi_split_path_info ^(.+\.php)(/.*)$;    include fastcgi_params;    fastcgi_param APP_ENV prod;    fastcgi_param APP_DEBUG 0;}

The doc page is a bit mean, because the respective bits are commented out.

If you want to simulate the production environment with the built-in webserver you can do it like this:

APP_ENV=prod APP_DEBUG=0 bin/console server:run

This requires the server-pack to be installed using composer and of course you can also set the command option --env as well, for the same effect.

And also make sure that you have checked .env and .env.local file too.

# prod config of .env or/and .env.localAPP_ENV=prodAPP_DEBUG=0