Unable to read environment variables

问题

I have a simple Symfony project, using "symfony/dotenv": "4.3.*", in the composer.json and trying to read in the value of an environment variable.

This is my command:

var_dump($_ENV['MY_NEW_VAR']);

This is my .env file

MY_NEW_VAR=testing

Upon executing the command I get the following

string(7) "testing"

All good so far.... But now if I want to use environment variables to override the setting it returns an error. First I set the environment variable

export MY_NEW_VAR="something_else"

Then execute the command again, with the following results

[ErrorException]
Notice: Undefined index: MY_NEW_VAR

If I remove the environment variable using unset MY_NEW_VAR and execute the command again I get the value from the .env file

I would expect the environment variable to override the .env setting as explained in the comments of the .env file

# In all environments, the following files are loaded if they exist,
# the later taking precedence over the former:
#
#  * .env                contains default values for the environment variables needed by the app
#  * .env.local          uncommitted file with local overrides
#  * .env.$APP_ENV       committed environment-specific defaults
#  * .env.$APP_ENV.local uncommitted environment-specific overrides
#
# Real environment variables win over .env files.

Why does it not work with environment variables? Am I missing something?

回答1:

The code in your question is correct, so I'd wager the problem lies somewhere else.

There are many vagaries and inconsistencies about how getenv(), $_ENV and $_SERVER work. I have found $_SERVER to be more reliable in my experience, and many times it safer to check both. E.g. if you check the code on config/bootstrap.php for Symfony 4.3 you'll see stuff like this:

$_SERVER['APP_ENV'] = $_ENV['APP_ENV'] = ($_SERVER['APP_ENV'] ?? $_ENV['APP_ENV'] ?? null) ?: 'dev';

In any case, if your $_ENV superglobal is initially empty, it could be because on the variables_order setting. Check its value, and if doesn't include an E, prepend it to the existing value and with that it should be populated correctly.

The docs say that S is equivalent to ES...

In both the CGI and FastCGI SAPIs, $_SERVER is also populated by values from the environment; S is always equivalent to ES regardless of the placement of E elsewhere in this directive.

but I have not found it to be consistently so.

来源：https://stackoverflow.com/questions/57002564/unable-to-read-environment-variables

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