Use this Nginx configuration to properly run Symfony in production (online) and development (local) environments on Heroku.

nginx_app.conf.php

location / {
    # try to serve file directly, fallback to rewrite
    try_files $uri @rewriteapp;
}

location @rewriteapp {
    # rewrite all to app.php
    rewrite ^(.*)$ /app<?php echo getenv('SYMFONY_ENV') === 'prod' ? '' : '_dev'; ?>.php/$1 last;
}

location ~ ^/(app|app_dev|config)\.php(/|$) {
    try_files @heroku-fcgi @heroku-fcgi;
    internal;
}