Use variables

Get a list of all variables defined on a given environment in the Console or use the CLI:

$ platform var
Variables on the project Example (abcdef123456), environment main:
| Name | Level   | Value | Enabled |
| foo  | project | bar   | true    |

Access variables in a shell 

Project and environment variables with the prefix env: are available as Unix environment variables in all caps. Access these variables and variables directly like this:

$ echo $FOO
Sample Project

Other project and environment variables are listed together in the PLATFORM_VARIABLES variable as a base64-encoded JSON object. Access them like this:

$ echo $PLATFORM_VARIABLES | base64 --decode
{"theanswer": "42"}

You can also get the value for a single variable within the array, such as with this command, which uses the jq processor:

$ echo $PLATFORM_VARIABLES | base64 --decode | jq '.theanswer'

Variable availability depends on the type and configuration. Variables available during builds can be accessed in build hooks and those available at runtime can be accessed in deploy hooks.

Access variables in your app 

To access environment variables in your app, you can use the Config Reader for the given language:

Alternative, use a built-in method for the given language.


// A simple variable.
$projectId = getenv('PLATFORM_PROJECT');

// An encoded JSON object.
$variables = json_decode(base64_decode(getenv('PLATFORM_VARIABLES')), TRUE);
import os
import json
import base64

# A simple variable.
project_id = os.getenv('PLATFORM_PROJECT')

# An encoded JSON object.
variables = json.loads(base64.b64decode(os.getenv('PLATFORM_VARIABLES')).decode('utf-8'))
const { env } = process;

// Utility to assist in decoding a packed JSON variable.
function read_base64_json(varName) {
  try {
    return JSON.parse(Buffer.from(env[varName], "base64").toString());
  } catch (err) {
    throw new Error(`no ${varName} environment variable`);

// A simple variable.
const projectId = env.PLATFORM_PROJECT;

// An encoded JSON object.
const variables = read_base64_json('PLATFORM_VARIABLES');
# A simple variable.
project_id = ENV["PLATFORM_PROJECT"] || nil

# An encoded JSON object.
variables = JSON.parse(Base64.decode64(ENV["PLATFORM_VARIABLES"]))
import com.fasterxml.jackson.databind.ObjectMapper;

import java.util.Base64;
import java.util.Map;

import static java.lang.System.getenv;
import static java.util.Base64.getDecoder;

public class App {

    public static void main(String[] args) throws IOException {
        // A simple variable.
        final String project = getenv("PLATFORM_PROJECT");
        // An encoded JSON object.
        ObjectMapper mapper = new ObjectMapper();
        final Map<String, Object> variables = mapper.readValue(
                String.valueOf(getDecoder().decode(getenv("PLATFORM_VARIABLES"))), Map.class);

Access complex values 

Variables can have nested structures. The following example shows nested structures in an app configuration:

        BASIC: "a string"
            - 'peanut butter'
            - 'jelly'
            "milk": "1 liter"
            "cookies": "1 kg"
        STEPS: ['un', 'deux', 'trois']
            red: '#FF0000'
            green: '#00FF00'
            blue: '#0000FF'

You can access these nested variables as follows:

$ echo $BASIC
a string
["peanut butter", "jelly"]
{"cookies": "1 kg", "milk": "1 liter"}
$ echo "$PLATFORM_VARIABLES" | base64 --decode | jq '."stuff:STEPS"'
$ echo "$PLATFORM_VARIABLES" | base64 --decode | jq '."stuff:COLORS"'
  "blue": "#0000FF",
  "green": "#00FF00",
  "red": "#FF0000"
// string(8) "a string"

// string(26) "["peanut butter", "jelly"]"

// string(38) "{"milk": "1 liter", "cookies": "1 kg"}"

$variables = json_decode(base64_decode($_ENV['PLATFORM_VARIABLES']), TRUE);

array(3) {
  string(2) "un"
  string(4) "deux"
  string(5) "trois"

array(3) {
  string(7) "#FF0000"
  string(7) "#00FF00"
  string(7) "#0000FF"
import os
import json
import base64

print os.getenv('BASIC')
# a string

print os.getenv('INGREDIENTS')
# ["peanut butter", "jelly"]

print os.getenv('QUANTITIES')
# {"milk": "1 liter", "cookies": "1 kg"}

variables = json.loads(base64.b64decode(os.getenv('PLATFORM_VARIABLES')).decode('utf-8'))

print variables['stuff:STEPS']
# [u'un', u'deux', u'trois']
print variables['stuff:COLORS']
# {u'blue': u'#0000FF', u'green': u'#00FF00', u'red': u'#FF0000'}

const { "stuff:STEPS": stuffSteps, "stuff:COLORS": stuffColors } = JSON.parse(
  Buffer.from(PLATFORM_VARIABLES, "base64").toString()

// "a string"
// ["peanut butter", "jelly"]
// {"cookies": "1 kg", "milk": "1 liter"}
// [ 'un', 'deux', 'trois' ]
// { blue: '#0000FF', green: '#00FF00', red: '#FF0000' }

Use variables also provides a series of variables to inform your app about its runtime configuration. They’re mostly prefixed with PLATFORM_ to differentiate them from user-provided values. You can’t set or update them directly.

The most important of these variables is the relationship information in PLATFORM_RELATIONSHIPS, which tells the app how to connect to databases and other services defined in services.yaml.

The following table presents all available variables and whether they’re available at build time (during build hooks) and at runtime.

Variable name Build Runtime Description
PLATFORM_APP_DIR Yes Yes The absolute path to the app directory.
PLATFORM_APPLICATION Yes Yes A base64-encoded JSON object that describes the app. It maps certain attributes from your app configuration, some with more structure. See notes.
PLATFORM_APPLICATION_NAME Yes Yes The app name as set in your app configuration.
PLATFORM_BRANCH No Yes The name of the Git branch.
PLATFORM_CACHE_DIR Yes No The directory where files are cached from one build to the next. The directory is shared among all branches, so the same cache is used for all environments.
PLATFORM_DOCUMENT_ROOT No Yes The absolute path to the web document root, if applicable.
PLATFORM_ENVIRONMENT No Yes The name of the environment.
PLATFORM_ENVIRONMENT_TYPE No Yes The environment type of the environment (development, staging, or production).
PLATFORM_OUTPUT_DIR Yes No The output directory for compiled languages at build time. Equivalent to PLATFORM_APP_DIR in most cases.
PLATFORM_PROJECT Yes Yes The project ID.
PLATFORM_PROJECT_ENTROPY Yes Yes A random, 56-character value created at project creation and then stable throughout the project’s life. Can be used for Drupal hash salts, Symfony secrets, and other similar values.
PLATFORM_RELATIONSHIPS No Yes A base64-encoded JSON object of relationships. The keys are the relationship name and the values are arrays of relationship endpoint definitions. The exact format is defined differently for each service.
PLATFORM_ROUTES No Yes A base64-encoded JSON object that describes the routes for the environment. It maps the content of your routes configuration.
PLATFORM_SMTP_HOST No Yes The SMTP host to send email messages through. Is empty when mail is disabled for the current environment.
PLATFORM_SOURCE_DIR Yes No Equivalent to PLATFORM_APP_DIR in the context of a running source operation. The directory contains a writable copy of your repository that you can commit to during the operation.
PLATFORM_TREE_ID Yes Yes The ID of the tree the application was built from, essentially the SHA hash of the tree in Git. Use when you need a unique ID for each build.
PLATFORM_VARIABLES Some Some A base64-encoded JSON object with all user-defined project and environment variables that don’t use a prefix. The keys are the variable names and the values are the variable values. Availability during builds and at runtime depends on the settings for each variable. See how to access individual variables.
PORT No Yes A string representing the port to which requests are sent if the web.upstream.socket_family property is unset or set to tcp.
SOCKET No Yes A string representing the path to the Unix socket file to use if the web.upstream.socket_family property is set to unix.

Variables on Dedicated Gen 2 environments 

Dedicated Gen 2 instances also have the following variables available:

Variable name Build Runtime Description
PLATFORM_CLUSTER No Yes The cluster ID. In older Dedicated Gen 2 instances, this is used to get the project ID. When several projects are linked, this provides the main project/cluster they’re linked to, while PLATFORM_PROJECT offers the specific project ID.
PLATFORM_MODE No Yes enterprise in all Dedicated Gen 2 production and staging environments. Note that an Enterprise support plan doesn’t always imply a Dedicated Gen 2 environment, but a Dedicated Gen 2 environment always implies an Enterprise support plan.

Distinguish Dedicated Gen 2 environment types 

While both production and staging Dedicated Gen 2 environments have enterprise for the PLATFORM_MODE variable, you can distinguish them by environment type. Make sure that the environment type is set correctly via the CLI or Console. Then run different code based on the type:

if [ "$PLATFORM_ENVIRONMENT_TYPE" = production ] ; then
    echo "This is live on production"
else if [ "$PLATFORM_ENVIRONMENT_TYPE" = staging ] ; then
    echo "This is on staging"
    echo "We're on development"


The PLATFORM_APPLICATION variable is available both at build time and in the runtime environment. But the specific attributes it contains differ in each case.

Each environment’s build is associated with a configuration ID that identifies it uniquely so builds can be reused. The ID is a product of your app code and some of its configuration for Not every attribute your app configuration is relevant to the build. Only those attributes that are relevant to builds are accessible at build time from PLATFORM_APPLICATION.

Attributes that are not available in PLATFORM_APPLICATION during builds:

  • Everything under resources
  • size
  • disk
  • Everything under access
  • Everything under relationship
  • Everything under firewall
  • hooks.deploy and hooks.post_deploy
  • Everything under crons
  • Everything under web, except web.mounts
  • Everything under workers, except workers.mounts

These attributes aren’t visible during build because they aren’t included as a part of the configuration component of the build slug. So modifying these values in your app configuration doesn’t trigger an app rebuild, only a redeploy. For more information, read about how builds work.

Use variables in static files 

Some apps require configuration values to be specified in a static, non-executable file (such as a .ini, .xml, or .yaml file) and don’t support reading from environment variables.

To populate these files with variables you set yourself, make sure the variables are set to be visible at build time.

The files can’t be populated with variables not available at build time (such as PLATFORM_RELATIONSHIPS). You also can’t write to them in a deploy hook as the file system is read only.

One workaround is to create a symbolic link to a writable location and then write to it in a deploy hook. The following example shows the process, though you have to modify it to fit your needs.

  1. Create a mount that isn’t accessible to the web in your app configuration:

            source: local
            source_path: config
  2. Create a symbolic link from the config file the application wants to a location in that mount:

    # From the application root...
    ln -s config/db.yaml db.yaml

    This example assumes the app wants a db.yaml file in its root for configuration.

  3. Commit the symbolic link and an empty config directory to Git.

  4. Configure a script to read from environment variables and write to config/db.yaml. Create a file with a shell script similar to this:
    # Ensure the file is empty.
    cat '' > config/db.yaml
    # Map the database information from the PLATFORM_RELATIONSHIPS variable into the YAML file.
    # Use this process to use whatever variable names your app needs.
    printf "host: %s\n" $(echo $PLATFORM_RELATIONSHIPS | base64 --decode | jq -r ".database[0].host") >> config/db.yaml
    printf "user: %s\n" $(echo $PLATFORM_RELATIONSHIPS | base64 --decode | jq -r ".database[0].username") >> config/db.yaml
  5. Call the script from the deploy hook your app configuration:

        deploy: |

Now, when your app starts and attempts to parse db.yaml, the symbolic link redirects it to config/db.yaml. Your script writes to that file on each deploy with updated information. Your app reads the exported values and proceeds as expected.