Run composer:

composer install

Build container:

# build container
docker build -t symfony-docker .

Check container env vars inside docker with .env file being passed:

docker run -it --rm -v "$PWD":/app --env-file=.env -w "/app" symfony-docker sh -c "bin/console debug:container --env-vars"

In EnvVarProcessor.php line 183:

Invalid JSON in env var "APP_JSON": Syntax error

and without passing .env file:

docker run -it --rm -v "$PWD":/app -w "/app" symfony-docker sh -c "bin/console debug:container --env-vars"

Symfony Container Environment Variables

---

Name Default value Real value

---

APP_JSON n/a "{"a":1}"
APP_SECRET n/a "cb4b2a7cbe10bc3d00659f42c67955f7"

---

The problem is parsing .env by docker, so making APP_JSON='{"a":1}' to be APP_JSON={"a":1} works for docker, but wouldn't work in console:

docker run -it --rm -v "$PWD":/app --env-file=.env -p 8000:8000 -w "/app" symfony-docker sh -c "echo \$APP_JSON"

'{"a":1}'

When replacing APP_JSON='{"a":1}' with APP_JSON={"a":1} it is the opposite - no error when passing .env, error if .env is ready by Symfony.

sed -i -e 's/APP_JSON=.*/APP_JSON={"a":1}/' .env

(OPTIONAL) Uncomment lines in Dockerfile and run the below to see WEB errors:

# run symfony
docker run -it --rm -v "$PWD":/app --env-file=.env -p 8000:8000 -w "/app" symfony-docker sh -c "/root/.symfony/bin/symfony server:start"

Now check http://127.0.0.1:8000/ and see the following error:

Cannot resolve argument $appJson of "App\Controller\DefaultController::index()": Invalid JSON in env var "APP_JSON": Syntax error

But when avoiding setting env vars in docker from .env, file is parsed by DotEnv and all works fine:

docker run -it --rm -v "$PWD":/app -p 8000:8000 -w "/app" symfony-docker sh -c "/root/.symfony/bin/symfony server:start"