Variables overview

Variables give you control over your projectโ€™s build process and runtime environment. You can set them in your code to make changes across your project or independent of the code for environment-specific settings.

In this way, your app has additional information, such as database credentials, the host or port it can use, and which server to connect to.

Variable types 

You can set variables at different levels. All variables can be strings or base64-encoded JSON-serialized values.

The following table defines what types of variables are available to you:

Type Definer Scope Precedence Build Runtime Uses
Application Application Application 4 Yes Yes Non-secret values that are the same across all environments
Project User Project 3 Yes Yes Secret values that are the same across all environments, such as database credentials
Environment User Environment 2 Some Yes Values that vary by environment, such as which database to connect to or which payment API keys to use Pre-defined Environment 1 Some Yes For information about your project

If there are conflicts between variables with the same name, variables take precedence from 1 down. So values (1) override environment variables (2), which override project variables (3), which override application-provided variables (4).

All of the variables can also be overridden via script.

Choosing a variable type 

Choose how to set the variable based on what you are trying to do.

Some environment variables should be the same for all environments. For example:

  • Build tool versions. If you have scripts that use specific versions of build tools (such as a specific Node.js version), You want the tools to be versioned along with your code so you can track the impact of changes. Set those variables in the application.
  • Credentials for common services. If you have credentials for services shared across your environments, you don’t want to commit these secrets to code. Set them as sensitive project variables.

Other configurations should vary between environment types. For example:

  • Service configuration for databases and such. This information be read from the PLATFORM_RELATIONSHIPS variable. It varies by environment automatically.
  • Mode toggles such as enabling debug mode, disabling certain caches, and displaying more verbose errors. This information might vary by environment type and should be set on the environment level.
  • API keys for remote services, especially payment gateways. If you have a different payment gateway for production and for testing, set its keys on the environment level.


If the names of variables at different levels match, an environment variable overrides a variable with the same name in a parent environment and both override a project variable. All variables can also be overridden via script.

For an example of how the different levels work, suppose you have the following inheritable variables defined for the main environment:

$ platform var -e main
Variables on the project Example (abcdef123456), environment main:
| Name           | Level       | Value  | Enabled |
| system_name    | project     | Spiffy |         |
| system_version | project     | 1.5    |         |
| api_key        | environment | abc123 | true    |
| debug_mode     | environment | 1      | true    |

And the following variables defined for the feature-x environment, a child environment of main:

$ platform var -e feature-x
Variables on the project Example (abcdef123456), environment feature-x:
| Name           | Level       | Value  | Enabled |
| system_name    | project     | Spiffy |         |
| system_version | project     | 1.5    |         |
| api_key        | environment | def456 | true    |
| system_version | environment | 1.7    | true    |

In the main environment, you can access $PLATFORM_VARIABLES:

echo $PLATFORM_VARIABLES | base64 --decode | jq

The output looks like this:

    "system_name": "Spiffy",
    "system_version": "1.5",
    "api_key": "abc123",
    "debug_mode": "1"

While in the feature-x environment, it looks like this:

    "system_name": "Spiffy",
    "system_version": "1.7",
    "api_key": "def456",
    "debug_mode": "1"

To get a visual overview of which variables are overridden in an environment, navigate in the Console to that environment’s variables settings. This example shows how it looks within the feature-x environment:

The Console showing the variables split into environment and project ones, with the environment variables api_key and system_version labeled as overridden and debug_mode as inherited the project variable system_version labeled as inactive.

Project variables that conflict with environment variables are labeled as Inactive. Environment variables are labeled as Inherited when they get their value from a parent environment and as Overridden when there is a conflict and the parent environment’s value doesn’t apply.

Variable prefixes 

Certain variable name prefixes have special meanings. Some are defined by and apply automatically. Others are just available as a convention for your application code to follow.

Top-level environment variables 

By default, project and environment variables are only added to the $PLATFORM_VARIABLES environment variable. You can also expose a variable as its own environment variable by giving it the prefix env:.

For example, the variable env:foo creates an environment variable called FOO. (Note the automatic upper-casing.)

platform variable:create --name env:foo --value bar

You can then access that variable directly in your app container:

$ echo $FOO

PHP-specific variables 

Any variable with the prefix php: is added to the php.ini configuration for all PHP-based application containers in the project.

For example, an environment variable named php:display_errors with the value On is equivalent to placing the following in php.ini:

display_errors = On

This feature is primarily useful to override debug configuration on development environments, such as enabling errors and configuring the Xdebug extension.

To apply a setting to all environments or have a setting differ among multiple PHP containers in one project, specify the variables in the file for your application. See the PHP configuration page for more information.

Framework-specific variables 

For specific frameworks, you can implement logic to override global configurations with environment-specific variables.

The Drupal templates show examples of logic mapping variables to Drupal’s configuration system. You can apply similar logic for other frameworks.

For Drupal 8+, any variable that begins with drupal: or d8settings: is mapped to the global $settings array, for low-level configuration. Any variable that begins with d8config: is mapped to the global $config array, which is useful for overriding Drupal’s exportable configuration system. In this case, the variable name needs two colons, one for d8config: and one for the name of the configuration object to override. For example, a variable named overrides the name property of the configuration object.