Env Var processors allow to transform the value of environment variables before using them in the Symfony app configuration. They are useful for example to transform the type of the env var (which, by definition is always a string) into a more suitable type, such as an integer or a boolean. In Symfony 4.3 we added new processors to provide new transformations.

Default Env Var Processor¶

Contributed by
Jérémy Derussé
in #28976.

It returns a default value when the given env var is not defined. It uses this syntax: env(default:DEFAULT_VALUE:ENV_VAR_NAME). You can combine it with any of the other env vars to do advanced things like the following:

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# config/services.yamlparameters:private_key:'%env(default:default_key:file:PRIVATE_KEY)%'default_key:'%env(PRIVATE_KEY)%'

Trim Env Var Processor¶

Contributed by
Maxime Steinhausser
in #29781.

It applies the trim() PHP function to the value of the env var before returning it. It's especially useful in combination with the file processor, as it'll remove newlines at the end of a file:

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# config/services.yamlparameters:private_key:'%env(trim:file:PRIVATE_KEY)%'