Note: This article is just a personal translation of another article on the AFSY website, originally in French, that I wrote when they organized an Advent calendar with various other cool PHP/Symfony developers!

Deploy a Symfony Flex project on Heroku

We well talk about three subjects here:

  • What is Flex?
  • Heroku, what’s that?
  • Let’s create our project and deploy it!

What is Flex?

Flex, also called Symfony Flex, is a Composer plugin you can install in any PHP project, and that will allow you to get a standardized structure and composition workflow.

Other articles might exist about Flex, especially on Fabien Potencier’s blog, so we won’t dig to deep in this.

In a few words we can tell that Flex:

  • Allows to use some aliases to install one or multiple packages (like cli for symfony/console or orm for many packages related to Doctrine ORM).
  • Allows automatization of default package configuration installation via recipes that can be defined in the public repositories symfony/recipes-contrib and symfony/recipes
  • Thanks to the new Symfony 4 & Flex structure, totally standardizes the structure of a PHP project and enforces the use of environment variables and automated Composer scripts.

Heroku, what’s that?

It is a platform that we can use for cloud computing purposes.

We can use it to host databases, applications (web, workers, etc.) and orchestrate all of them.

Its configuration can be handled via a command-line application or an online dashboard, both very accessible.


Heroku is not entirely free: there is a free plan available until a certain number hours of use that renews every month. In the case of a web application, it enters in a “sleeping” state after 30 minutes of inactivity, saving remaining free time. The free plan is therefore very useful for prototypes or CI environments.

For the rest, the price depends on the performances you want, add-ons you use, and mostly the amount of time apps are run.

For example, the Hobby plan is $7 per month, but it will cost you only $3.50 if you use it 15 days and stop it afterwards. This is really important to know, because the bill will be calculated based on the uptime of each of your Dynos (we’ll talk about this later).

A Heroku server

Heroku machines use a Linux distribution named Cedar, based on Ubuntu, and we can configure an application to use Cedar 14.04 or Cedar 16.04 (the last Ubuntu LTS branches).

Applications are executed in Linux containers called Dynos.

There are three types of Dynos: web, worker and one-off, and they are all configured by a single file named Procfile.

  • web dynos are executed in a persistent way, configured by your Procfile, and they are the only ones to be able to receive HTTP requests sent to your application. You can have only one single web dyno at a time.
  • worker dynos are scripts you configure in your Procfile and are mostly used as background tasks, like queues.
  • one-off dynos are temporary dynos created, for example, when manually executing scripts with the heroku run {script...} command. They are also used when deploying a new release, and by the Heroku Scheduler addon, used to manage background tasks (similarly to crontab, check the example at the bottom of this article if you need).

Whatever script you have in your Procfile, it will always be executed in a Dyno.

Customize our server

As a user, we do not have access to the distribution. We then cannot modify the machine’s packages.

However, Heroku uses a system buildpacks that can execute commands in the machine to install some packages.


Buildpacks include a set of scripts having various responsibilities:

  • Detect your application “type” (Ruby, PHP, Javascript, etc.).
  • Compile your application by executing scripts (install dependencies, etc.).
  • Update your Heroku configuration after installation, like install add-ons or change the default script to execute on a dyno (they mostly provide entrypoints for this).

For example, the PHP buildpack is automatically detected if a composer.json file is present at the root of your project.

It is also capable of installing PHP extensions if they are specified in the require section of your composer.json file, like "require": { "ext-intl": "*" } for instance.

Buildpacks are essential to a base application configuration. Unless you just execute bash scripts…


Add-ons are usually used to integrate your project with external services, like databases, log reports, profiling, email sender…

Most add-ons offer a free plan with limited performances, but perfectly suitable for small projects.

They have several advantages:

  • They are capable of adding environment vars to your config so you can use them in your project.
  • They detach the application and services, like putting the database in an external server, easing maintenance and saving us from outsourcing all the stack ourselves.
  • And, like other cloud computing services (like SensioCloud), this works like a charm with the last good practices of Symfony that recommend using environment vars.

Most of the time, you will need add-ons, at least for database and sending e-mails, and the free plan will be fairly enough for simple projects needing few resources

Create a Symfony 4 project with Flex

Now that we know what are the tools we are going to use, let’s use them!

First, let’s create the project somewhere on our machine:

$ composer create-project symfony/skeleton:^4.0 my_project

The symfony/skeleton package contains one single thing: a composer.json file, requiring some packages to create a project with Symfony, such as Flex.

Main dependencies that ease everything are the following:

  • symfony/flex: the Composer plugin we were talking about in the beginning of this article.
  • symfony/framework-bundle: The main package that is used to create a Symfony project.
  • symfony/lts: A simple Composer package allowing us to define which major Symfony version we’ll use. This package simply defines conflicts with the next major version, avoiding using incompatible packages.

The big advantage is that the symfony/framework-bundle package has a Flex recipe that will initialize nice tools in our project:

  • Default framework configuration in the config/ directory.
  • A web front-controller in the public/ directory.
  • A pre-configured micro-kernel in src/Kernel.php.
  • Environment set in .env and .env.dist files to set up our project’s main configuration.
  • An already working .gitignore.
  • Composer scripts to clear the cache and install assets on every composer install/update call.

Given that symfony/console is a base dependency of the symfony/skeleton package, Flex will also install the symfony/console recipe and add the bin/console file we use to know for our Symfony projects.

All these actions are defined in the different recipes of the installed packages, and the advantage is that, thanks to Flex, if we delete a package, all that have been installed by the recipe will be removed too! No more need to bother about removing bundles or config files.

Create a git environment

This is mandatory for every project!

$ git init

We will use it later, but at least we set up the field to work with Git.

Install Symfony native web server

To test our project, no need for a Nginx or Apache configuration! Like before, Symfony has the WebServerBundle so we can test our project using native PHP 5.4 built-in server in development. But it’s not shipped by default, let’s install it:

$ composer require --dev server

server is simply an alias of symfony/web-server-bundle, thanks Flex again!

Create a default controller

This controller is mandatory, because there is no more default controller in Symfony.


// src/Controller/DefaultController.php

namespace App\Controller;

use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Annotation\Route;

class DefaultController
     * @Route("/", name="homepage")
    public function index(): Response
        return new Response('It works! ☺');

Of course, we are using annotations, so we need them:

$ composer require annotations

This will install packages and bundles that are necessary to use annotations, especially Routing ones.

Test this configuration

Let’s execute the command from WebServerBundle to see our website:

$ php bin/console server:run

 [OK] Server listening on

 // Quit the server with CONTROL-C.

This should give something like this:

localhost default working project

Great! It works, so we can say that we have an operational Symfony project!

Install Heroku command-line

Now we will start working on deployment with Heroku.

First, we need to install the CLI tool provided by Heroku:

Once installed, we can run it to check it works:

$ heroku --version
heroku-cli/6.14.36-15f8a25 (linux-x64) node-v8.7.0

Login with Heroku

Obviously, you should first create an account onHeroku, and once done, you have to log in with the CLI tool:

$ heroku login
Enter your Heroku credentials:
Password: *************█
Logged in as

This will help Heroku CLI to give us all details about our projects, their configuration, etc.

Starting from now, all heroku commands will be executed at the root of our project.

Create the project on Heroku

Heroku lets us do everything from the command-line, like creating a project:

$ heroku create
Creating app... done, stark-escarpment-87840 |

This gives us the final URL of the project (using the domain) and the final URL of the git remote to use.

Install the buildpack

We will install the PHP buildpack to automatize what we need:

$ heroku buildpacks:set heroku/php
Buildpack set. Next release on stark-escarpment-87840 will use heroku/php.
Run git push heroku master to create a new release using this buildpack.

Heroku proposes us to deploy a new release, but we will do this later, when the project is ready ☺.

Add Heroku branch as a remote

The goal is to deploy with a simple git push.

And the url was just given above by Heroku, let’s add it:

$ git remote add heroku

Note: naming the remote heroku allows Heroku CLI to automatically detect which project will be managed. Else, we would have to set it as a command-line option on every call.

Reach production

To open the URL of your project, we can simply call:

$ heroku open

We should see something like this:

heroku default home

Obviously, there’s nothing yet, because we didn’t deploy. But at least, Heroku heard our demands.

Add environment vars

First, we need to add environment vars Symfony told us to specify.

All references are in .env.dist, and each time we add a new var there, we have to add it on Heroku too, manually.

For now, only 2 vars are needed:

$ heroku config:set APP_ENV=prod APP_SECRET=Wh4t3v3r

Prepare the project for it to be compatible with Heroku

First, we need to create a Procfile.

The Procfile is a file that describes all the different Dynos our project will use.

Each dyno will count in the spent time for the current plan, so be careful: do not create dynos that will not be used often. For cron tasks, you have the Scheduler (see later).

Here, we only have one special dyno: web.

Each line contains two informations: the dyno name, that must be unique, and the script to execute.

web is the only special name, it is the only one receiving HTTP requests.

The script will be the one provided by the PHP buildpack, a nginx process followed by the web entry point directory.

web: vendor/bin/heroku-php-nginx public/

It’s enough for Heroku to execute our code.

You can also customize nginx and php-fpm configuration, but it’s just about reading the documentation, and we don’t need it yet.

Deploy the project on Heroku

Let’s deploy!

$ git add .
$ git commit -m "Initial files"
$ git push heroku master
remote: Compressing source files... done.
remote: Building source:
remote: -----> PHP app detected
remote: -----> Bootstrapping...
remote: -----> Installing platform packages...
remote:        - php (7.1.11)
remote:        - nginx (1.8.1)
remote:        - apache (2.4.29)
remote: -----> Installing dependencies...
remote:        Composer version 1.5.2 2017-09-11 16:59:25
remote:        Loading composer repositories with package information
remote:        Installing dependencies from lock file
remote:        Package operations: 40 installs, 0 updates, 0 removals
remote:        (...)
remote:        Generating optimized autoload files
remote:        (...)
remote:        Executing script cache:clear [OK]
remote:        Executing script assets:install --symlink --relative public [OK]
remote: -----> Preparing runtime environment...
remote: -----> Checking for additional extensions to install...
remote: -----> Discovering process types
remote:        Procfile declares types -> web
remote: -----> Compressing...
remote:        Done: 16.7M
remote: -----> Launching...
remote:        Released v13
remote: deployed to Heroku
remote: Verifying deploy... done.

Project is now deployed, let’s open it:

$ heroku open

We should see this:

heroku prod working

Now that the project is installed, we won’t stop here, won’t we?

Our projects are much more complex than a single PHP file, so let’s continue.

Install a database

Prepare the project

First, install the Doctrine ORM:

$ composer require orm-pack
Using version ^1.0 for symfony/orm-pack
Symfony operations: 3 recipes (7d946f30d2601a4530d4c10790aefad1)
  - Configuring doctrine/doctrine-cache-bundle (1.3.2): From auto-generated recipe
  - Configuring doctrine/doctrine-bundle (1.6): From
  - Configuring doctrine/doctrine-migrations-bundle (1.2): From

The different Flex recipes will configure this:

  • DoctrineBundle :
    • Adds the DATABASE_URL environment var to our .env file.
    • Default bundle configuration, using this var.
  • DoctrineMigrationsBundle :
    • Bundle configuration, and automatically discovered migrations in src/Migrations.

We’ll talk later about migrations.

Prepare Heroku database

We now need to install a database in Heroku, and we’ll use an add-on for this:

$ heroku addons:create heroku-postgresql:hobby-dev
Creating heroku-postgresql:hobby-dev on stark-escarpment-87840... free
Database has been created and is available
 ! This database is empty. If upgrading, you can transfer
 ! data from another database with pg:copy
Created postgresql-flexible-83322 as DATABASE_URL
Use heroku addons:docs heroku-postgresql to view documentation

Heroku will use another server (that we won’t care about) to manage the database, which eases managing and migrating, making backups, etc., while keeping our app in its own place.

Note: I’m using PostgreSQL here because Heroku recommends it and it has nice stuff regarding pgsql, but you can also use other add-ons for MySQL or MariaDB, like ClearDB or JawsDB providers, which are also external cloud services and can be integrated to Heroku just as heroku-postgresql.
We then must update our .env and .env.dist file locally to change the PDO driver from mysq (used by default in the ORM) to pgsql.

Since the env var is already added to Heroku, we can check it in case of:

$ heroku config
=== stark-escarpment-87840 Config Vars
APP_ENV:      prod
APP_SECRET:   Wh4t3v3r
DATABASE_URL: postgres://...  <--- This var was just added by heroku-postgresql add-on.

Note: The presented addons for MySQL and MariaDB can have an environment var with a different name. Feel free to change your .env files and your Doctrine or Heroku config, to use it.

We now just have to create our entities like we are used to!

However, for the schema, it’s a good practice to use migrations.

Talking about migrations, how to execute them on Heroku?

Customize deployment scripts

Before talking about migrations, let’s first see how to customize our deploys.

Heroku checks uses buildpacks to determine what commands to execute when we create a new release.

As our project is mostly a PHP project, the PHP buildpack detects the presence of a script in the scripts section of our composer.json file: compile.

This script is executed when deploying, via composer run compile.

The advantage is that if this script fails with an exit code different than zero, the deployment is canceled!

We can therefore put our migrations there.

Create our migration

Let’s create our database and the first necessary migration.

$ php bin/console doctrine:database:create
$ php bin/console doctrine:migrations:diff

Note: This command works only if you have an empty database.
If you want to be sure the generated migration is correct, you can execute these commands, just in case:

$ php bin/console doctrine:database:drop --force
$ php bin/console doctrine:database:create
$ php bin/console doctrine:migrations:diff

Otherwise, create a migration with the doctrine:migrations:generate command, copy a dump of your database and copy/paste it directly in the generated migration file.

Once you’ve done that, you should have something like this:

<?php declare(strict_types = 1);

namespace DoctrineMigrations;

use Doctrine\DBAL\Migrations\AbstractMigration;
use Doctrine\DBAL\Schema\Schema;

 * Auto-generated Migration: Please modify to your needs!
class Version20171106100053 extends AbstractMigration
    public function up(Schema $schema)
        // this up() migration is auto-generated, please modify it to your needs
        $this->abortIf($this->connection->getDatabasePlatform()->getName() !== 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');

        $this->addSql('CREATE SEQUENCE Post_id_seq INCREMENT BY 1 MINVALUE 1 START 1');
        $this->addSql('CREATE TABLE Post (id INT NOT NULL, title VARCHAR(255) NOT NULL, content TEXT NOT NULL, PRIMARY KEY(id))');

    public function down(Schema $schema)
        // this down() migration is auto-generated, please modify it to your needs
        $this->abortIf($this->connection->getDatabasePlatform()->getName() !== 'postgresql', 'Migration can only be executed safely on \'postgresql\'.');

        $this->addSql('CREATE SCHEMA public');
        $this->addSql('DROP SEQUENCE Post_id_seq CASCADE');
        $this->addSql('DROP TABLE Post');

If your migration looks like this, let’s continue!

Add migrations to our deployment workflow

To execute our migrations, we need one single command:

$ php bin/console doctrine:migrations:migrate

                    Application Migrations

WARNING! You are about to execute a database migration that could result in schema changes and data lost. Are you sure you wish to continue? (y/n)y
Migrating up to 20171106100053 from 0

  ++ migrating 20171106100053


  ++ migrated (2.7s)


  ++ finished in 2.7s
  ++ 1 migrations executed
  ++ 2 sql queries

When executing this locally, everything works. Now we must execute it on production, and only when deploying.

We then will add a Composer script: the one the PHP buildpack executes at deploy time (see above).

    "scripts": {
        "compile": [
            "php bin/console doctrine:migrations:migrate"

That’s all!

On every deploy, this command will be executed in the application context. And as the context inherits from all environment vars, we do not even need to add --env=prod like we did during the old days.

And now, let’s deploy again:

$ git add . && git commit -m "Setup migrations"
$ git push heroku master
remote: -----> Running 'composer compile'...
remote:        > php bin/console doctrine:migrations:migrate
remote:                            Application Migrations
remote:        Migrating up to 20171106100053 from 0
remote:          ++ migrating 20171106100053
remote:             -> CREATE SEQUENCE Post_id_seq INCREMENT BY 1 MINVALUE 1 START 1
remote:             -> CREATE TABLE Post (id INT NOT NULL, title VARCHAR(255) NOT NULL, content TEXT NOT NULL, PRIMARY KEY(id))
remote:          ++ migrated (0.06s)
remote:          ------------------------
remote:          ++ finished in 0.06s
remote:          ++ 1 migrations executed
remote:          ++ 2 sql queries

Migrations have been executed on the production database managed by Heroku, everything’s ok!

Execute cron with Heroku and Symfony

First, we need a command to execute, let’s create a dummy one:


namespace App\Command;

use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;

class SimpleMessageCommand extends Command
    protected static $defaultName = 'app:simple-message';

    protected function configure()
        $this->setDescription('Simply sends a message to stdout and stderr.');

    protected function execute(InputInterface $input, OutputInterface $output)
        $now = date('Y-m-d H:i:s');
        $output->writeln("[$now] Stdout message");
        fwrite(STDERR, "[$now] Stderr message");

The goal is to check Heroku logs to see these messages.

Pro tip: Since Symfony 3.4, we can use the static property Command::$defaultName. If our command is defined as a service, this will allow Symfony to optimize console loading and container compilation by not instantiating the command everytime.

Instal Heroku Scheduler

Heroku Scheduler is the addon that will allow us to execute tasks at regular intervals.

We’ll install it in our project:

$ heroku addons:create scheduler:standard
Creating scheduler:standard on stark-escarpment-87840... free
This add-on consumes dyno hours, which could impact your monthly bill. To learn more:

To manage scheduled jobs run:
heroku addons:open scheduler

Created scheduler-reticulated-65091
Use heroku addons:docs scheduler to view documentation

Now, let’s open this addon in the browser to customize it:

$ heroku addons:open scheduler

You should see something like this:

Scheduler home

The Add new job button will help us to exactly what we need!

Scheduler job

The frequency is less flexible than a real cron task, but for most simple tasks, this remains the best option.
Else, we’ll need a worker, which is more complex to setup (and more expensive).

We then can execute our task:

  • Once a day, with a hour/half-past time.
  • Every hour, to the dozen minutes.
  • Every ten minutes after the task is created/updated.

Once your command is configured, you can wait a few minutes for it to execute.

Let’s use Heroku logs to check for this:

$ heroku logs | grep scheduler 
2017-12-01T21:02:56.302995+00:00 heroku[scheduler.8108]: Starting process with command `php bin/console app:simple-message`
2017-12-01T21:02:56.979408+00:00 heroku[scheduler.8108]: State changed from starting to up
2017-12-01T21:02:58.362544+00:00 app[scheduler.8108]: [2017-12-01 21:02:58] Stdout message
2017-12-01T21:02:58.482250+00:00 app[scheduler.8108]: [2017-12-01 21:02:58] Stderr message
2017-12-01T21:02:58.486752+00:00 heroku[scheduler.8108]: Process exited with status 0
2017-12-01T21:02:58.504268+00:00 heroku[scheduler.8108]: State changed from up to complete

(Note: On Windows, you don’t have grep, so just listen to the logs without grepping, it’s fine too!)

We see our Stdout and Stderr messages!

And voilà, we have a correctly configured routine!

Note: Be careful about the execution time of your tasks, because it will count in the consumed time of your dyno, and be charged depending on your billing plan. However, a command that takes only 5 seconds, executed 144 times a day, this makes 720 seconds consumed in a month. Nothing really big compared to the approximately 2592000 secondes for a web-server running 24/7.

Improve our Heroku environment

Heroku being full of addons, and most of them having a free plan, here are my recommendations:

  • Autobus, a backup system for your database, really useful and the free plan is ideal for simple projects.
  • Blackfire (beta), the unavoidable PHP profiling tool!
  • Mailgun, awesome mailer service, which can also be directly plugged to Swiftmailer thanks to the MAILER_URL environment var. And the free plan grants you 400 emails per day, (or approximately 12000 per month) is largely enough for most projects (the next plan being at 50000 mails per month…).
  • Papertrail, nice monitoring tool for logs for your dynos, very useful to keep an eye on PHP and web-server errors. It can send you an email periodically with a digest of all errors, and you have access to many filters, commands, etc.. The big advantage is that we don’t even have to configure Monolog with a complex setup: we just need to redirect all logs to php://stderr!
  • Deploy Hooks, a nice way to receive a small notification on Slack, IRC, email or an HTTP request on any url when the project is deployed and successfully released!


Heroku is a really simple PaaS tool to use, but above all, it’s awesome for testing, because we just have to use review apps for preprod, and as preprod is not always used, we can use the free plan for it!

For upload and file storage, the filesystem is temporary, so any upload is deleted after a release. No persistent mounting point is available (contrary to for example), but it’s really easy to setup file upload to Amazon S3, there’s even a documentation page for this, you just have to use S3 references in your code and you’re set.

For Symfony and S3, I am personally using the combo of oneup/flysystem-bundle and league/flysystem-aws-s3-v3, which allow me to just use the League\Flysystem\FilesystemInterface service as dependency to my own services/controllers, and it works like a charm!

At Studio Agate, we made the choice to use Heroku for our project, a big monolithic multi-domain web application that stores portals and websites related to the tabletop RPGs the studio makes, with a character manager, and an interactive cartography application.