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13.

Environment Variables

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Environment variables are for values that differ depending on the environment we're developing in, like locally vs production. The most common example of this is the database connection details. We can set real environment variables in our operating system, and while many cloud hosting platforms make it super easy to set these variables, it's not the easiest thing to do locally. Symfony also has this .env file which helps make life easy, especially during development.

Okay, here's the plan: We want our iss_location_cache_ttl value to be different locally versus on production. In our prod environment, we want our cache to last longer than the 5 seconds that we have now. The easiest way to do this would be to create a custom environment variable and set it to a different value for each environment - dev and prod.

In our .env file, down here, write ISS_LOCATION_CACHE_TTL in all uppercase letters, which is standard for environment variables. Let's set this to 5 by default. Now, over in services.yaml, we're going to keep the iss_location_cache_ttl parameter, but instead of 5, let's set it to the environment variable we just created. To do that, we need to leverage a special syntax. Write '%env()' and select our new ISS_LOCATION_CACHE_TTL environment variable. Nice!

To debug this, in /src/Controller/MainController.php, find homepage(). Inside that, below Response, let's write dd($this->getParameter()) and add iss_location_cache_ttl. Back at the browser, refresh. There's 5. It's subtle, but you may have noticed that this value is a string right now. All environment variable values are just simple strings by default, but Symfony has a way to typecast them to a different type. They're called "environment variable processors", and one of them can help us typecast this to an integer instead.

Back in our code, open services.yaml. Before the environment variable, add int:. If we go refresh... now we have a real integer 5. If we were deploying this project to production, we'd probably want to set this ISS_LOCATION_CACHE_TTL variable to something a little longer, like 60, so it will cache the data for 1 minute instead of 5 seconds. The shorter time frame is just more practical while we're testing things out.

While we're here, I want to talk about some other .env files. This .env file is committed to your Git repository, and as you see here, when I make changes to it, those changes are unstaged. So if you have some secrets that you don't want to commit to your Git repository, like sensitive tokens, passwords, etc, you can create a different file - .env.local. This one is ignored by Git, which we can see in our .gitignore file. Any sensitive info can be stored here and it won't be committed to the repository. We could, for example, move this APP_SECRET environment variable into our .env.local file. Inside our .env file, we can keep this empty or set it to some fake value. It's generally good practice to still keep the environment variables in the .env so that other developers can see them and set real values for them in their .env.local file. This was just an example, so we can change this back.

Along with these two files, there's also the less commonly used .env.test and .env.prod. Those are only loaded in the test and prod environments respectively. We also have a handy command to debug environment variables. At your terminal, run:

bin/console debug:dotenv

This can help us understand what order those files will be loaded in and, as a bonus, it lists all of the environment variables it found in each file. So far, we only have three and we can see their actual values and in which files those values are set.

If you're serious about securing your sensitive information, Symfony has a special tool for this called the "Secrets Vault". If you Google "Symfony secrets", one of the top results is "How to Keep Sensitive Information Secret", which leads us to some documentation. With the Secrets Vault, we can safely commit environment variables to our Git repository because they're encrypted and can't be read without decrypting. If you need this level of data protection, I encourage you to read the docs or check out our related videos on SymfonyCasts. I'll revert the changes we made to our homepage and remove this dd(). We don't need that anymore.

Next: Let's talk more about auto-configuration.