Preparing your Application

Deploying a Symfony application to Heroku doesn't require any change in its code, but it requires some minor tweaks to its configuration.

By default, the Symfony app will log into your application's app/log/ directory. This is not ideal as Heroku uses an ephemeral file system. On Heroku, the best way to handle logging is using Logplex. And the best way to send log data to Logplex is by writing to STDERR or STDOUT. Luckily, Symfony uses the excellent Monolog library for logging. So, a new log destination is just a change to a config file away.

Open the app/config/config_prod.yml file, locate the monolog/handlers/nested section (or create it if it doesn't exist yet) and change the value of path from "%kernel.logs_dir%/%kernel.environment%.log" to "php://stderr":

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# app/config/config_prod.yml
monolog:
    # ...
    handlers:
        # ...
        nested:
            # ...
            path: "php://stderr"

Once the application is deployed, run heroku logs --tail to keep the stream of logs from Heroku open in your terminal.

Creating a Procfile

By default, Heroku will launch an Apache web server together with PHP to serve applications. However, two special circumstances apply to Symfony applications:

1. The document root is in the web/ directory and not in the root directory of the application;
2. The Composer bin-dir, where vendor binaries (and thus Heroku's own boot scripts) are placed, is bin/ , and not the default vendor/bin.

Create a new file called Procfile (without any extension) at the root directory of the application and add just the following content:

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web: bin/heroku-php-apache2 web/

If you prefer working on the command console, execute the following commands to create the Procfile file and to add it to the repository:

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$ echo "web: bin/heroku-php-apache2 web/" > Procfile
$ git add .
$ git commit -m "Procfile for Apache and PHP"
[master 35075db] Procfile for Apache and PHP
 1 file changed, 1 insertion(+)

Setting the prod Environment

During a deploy, Heroku runs composer install --no-dev to install all of the dependencies your application requires. However, typical post-install-commands in composer.json, e.g. to install assets or clear (or pre-warm) caches, run using Symfony's dev environment by default.

This is clearly not what you want - the app runs in "production" (even if you use it just for an experiment, or as a staging environment), and so any build steps should use the same prod environment as well.

Thankfully, the solution to this problem is very simple: Symfony will pick up an environment variable named SYMFONY_ENV and use that environment if nothing else is explicitly set. As Heroku exposes all config vars as environment variables, you can issue a single command to prepare your app for a deployment:

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$ heroku config:set SYMFONY_ENV=prod

Pushing to Heroku

Next up, it's finally time to deploy your application to Heroku. If you are doing this for the very first time, you may see a message such as the following:

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The authenticity of host 'heroku.com (50.19.85.132)' can't be established.
RSA key fingerprint is 8b:48:5e:67:0e:c9:16:47:32:f2:87:0c:1f:c8:60:ad.
Are you sure you want to continue connecting (yes/no)?

In this case, you need to confirm by typing yes and hitting <Enter> key - ideally after you've verified that the RSA key fingerprint is correct.

Then, deploy your application executing this command:

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$ git push heroku master

Initializing repository, done.
Counting objects: 130, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (107/107), done.
Writing objects: 100% (130/130), 70.88 KiB | 0 bytes/s, done.
Total 130 (delta 17), reused 0 (delta 0)

-----> PHP app detected

-----> Setting up runtime environment...
       - PHP 5.5.12
       - Apache 2.4.9
       - Nginx 1.4.6

-----> Installing PHP extensions:
       - opcache (automatic; bundled, using 'ext-opcache.ini')

-----> Installing dependencies...
       Composer version 64ac32fca9e64eb38e50abfadc6eb6f2d0470039 2014-05-24 20:57:50
       Loading composer repositories with package information
       Installing dependencies from lock file
         - ...

       Generating optimized autoload files
       Creating the "app/config/parameters.yml" file
       Clearing the cache for the dev environment with debug true
       Installing assets using the hard copy option
       Installing assets for Symfony\Bundle\FrameworkBundle into web/bundles/framework
       Installing assets for Acme\DemoBundle into web/bundles/acmedemo
       Installing assets for Sensio\Bundle\DistributionBundle into web/bundles/sensiodistribution

-----> Building runtime environment...

-----> Discovering process types
       Procfile declares types -> web

-----> Compressing... done, 61.5MB

-----> Launching... done, v3
       http://mighty-hamlet-1981.herokuapp.com/ deployed to Heroku

To git@heroku.com:mighty-hamlet-1981.git
 * [new branch]      master -> master

And that's it! If you now open your browser, either by manually pointing it to the URL heroku create gave you, or by using the Heroku Toolbelt, the application will respond:

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$ heroku open
Opening mighty-hamlet-1981... done

You should be seeing your Symfony application in your browser.