… (soufianZantar)

This PR was merged into the 3.4 branch.

Discussion
----------

[Dotenv] search variable values in ENV first then env file

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | yes
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | #32595
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!-- required for new features -->

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 - Bug fixes must be submitted against the lowest maintained branch where they apply
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 - Features and deprecations must be submitted against branch 4.4.
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I think we must searhing the value of variables in $_ENV before the .env file to fix this issues.
before this fix Parse method will return the value in .env file and not the value passed in this command `composer dump-env prod `.

**the issue:**

In my .env file, I have a variable TEST that depends on the APP_ENV variable like this:

```
# .env file

###> symfony/framework-bundle ###
APP_ENV=dev
APP_SECRET=2eb810c79fba0dd5c029a2fa53bfdb51
###< symfony/framework-bundle ###

TEST=foo_${APP_ENV}

```
I run composer dump-env dev command to generate my .env.locale.php, everything works fine, the value of my variable TEST is correct.

```
// .env.locale.php

return array (
  'APP_ENV' => 'dev',
  'TEST' => 'foo_dev',
  'APP_SECRET' => '2eb810c79fba0dd5c029a2fa53bfdb51',
);
```
Then I run the same command with prod environment (composer dump-env prod), the value of TEST is wrong (it is same as for dev)

```
// .env.locale.php

return array (
  'APP_ENV' => 'prod',
  'TEST' => 'foo_dev',
  'APP_SECRET' => '2eb810c79fba0dd5c029a2fa53bfdb51',
);
```

Commits
-------

3018041 [Dotenv] search variable values in ENV first then env file