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Environment variables are for values that differ dependingon the environment we're developing in, like locally vs production.The most common example of this is the database connection details.We can setreal 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 ouriss_location_cache_ttl valueto be differentlocally versus on production.In ourprod environment, we want our cache to lastlonger than the 5 seconds that we have now.

The easiest way to do this would be to create acustom environment variable and set itto a different value for each environment -dev andprod.

Creating and Reading Environment Variables

In our.env file, down here, writeISS_LOCATION_CACHE_TTL in all uppercase letters,which is standard for environment variables.Let's set this to5 by default.

Now, over inservices.yaml, we're going to keep theiss_location_cache_ttl parameter,but instead of5, 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 newISS_LOCATION_CACHE_TTL environment variable.Nice!

To debug this,in/src/Controller/MainController.php, findhomepage().Insidethat, belowResponse, let's writedd($this->getParameter())and addiss_location_cache_ttl.

Environment Variable Processors

Back at the browser, refresh.There's5.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 waytotypecast them to adifferent type.They're called "environment variable processors",and one of them can help us typecast this to an integer instead.

Back in our code, openservices.yaml.Before the environment variable, addint:.

If we go refresh...now we have a real integer5.If we were deploying this project to production, we'd probably wantto set thisISS_LOCATION_CACHE_TTL variable to something a little longer, like60,so it will cache the data for1 minute instead of 5 seconds.The shorter time frame is just more practical while we're testing things out.

The.env.local File

While we're here, I want to talk about someother.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 somesecrets that you don't want to commit to your Git repository,like sensitive tokens, passwords, etc, you can create adifferent file -.env.local.This one isignored 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 thisAPP_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.envso that other developers can see them and set real values for them intheir.env.local file.This was just an example, so we can change this back.

Debugging Environment Variables

Along with these two files, there's also the less commonly used.env.test and.env.prod.Those are only loaded in thetest andprod 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 thosefiles 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 valuesand in which files those values are set.

If you'reserious about securing your sensitive information, Symfony has a special toolfor this called the "Secrets Vault".If you Google "Symfony secrets", one of the top results is "Howto Keep Sensitive Information Secret", which leads us to some documentation.With the Secrets Vault, we can safely commit environment variables to our Git repositorybecause they're encrypted andcan't be read withoutdecrypting.If you need this level of data protection, I encourage you to read the docs or checkout our related videos on SymfonyCasts.I'll revert the changes we made to our homepage and remove thisdd().We don't need that anymore.

Next: Let's talk more aboutauto-configuration.

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