environment.md

Environment variables

Maybe you want to set a feature flag by an environment variable. In Symfony 3.4 you can set and cast env variables very simple. But in symfony versions before that, it's not that easy. Therefore, you can set in the config whether the active status is to be pulled from an environment variable.

Just give the variable name in the env parameter:

# config.yml

flagception:
    features:      
    
        # This feature check the env var 'FEATURE_NAME_FROM_ENV'
        # setenv('FEATURE_NAME_FROM_ENV=false')
        feature_123:
            env: FEATURE_NAME_FROM_ENV  

You can combine all parameter together. First the default value is checked. If the value is false, the value from env is checked. If this also returns false, the constraints are checked.

# config.yml

flagception:
    features:      
        feature_123:
            default: false
            env: FEATURE_NAME_FROM_ENV  
            constraint: 'user_role == ROLE_ADMIN'

As alternative, you can use the %env()% syntax for the default field:

# config.yml

flagception:
    features:      
        feature_123:
            default: '%env(FEATURE_NAME_FROM_ENV)%'