bug symfony#22500 [DotEnv] Don't override existing $_SERVER vars (Pierstoval, javiereguiluz)

This PR was merged into the 3.3-dev branch.

Discussion
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[DotEnv] Don't override existing $_SERVER vars

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#22493
| License       | MIT
| Doc PR        | ~

As of symfony#22493 I decided to make a PR in order to add a specific test just for this behavior and make sure we never touch `$_SERVER` predefined variables.

Commits
-------

e575831 Update a test value for consistency
0a95d89 Minor changes to make tests more readable
3bf7e49 [DotEnv] Don't override existing $_SERVER vars

Author: fabpot

src/Symfony/Component/Dotenv/Dotenv.php

@@ -67,7 +67,7 @@ public function load($path/*, ...$paths*/)
     public function populate($values)
     {
         foreach ($values as $name => $value) {
-            if (isset($_ENV[$name]) || false !== getenv($name)) {
+            if (isset($_ENV[$name]) || isset($_SERVER[$name]) || false !== getenv($name)) {
                 continue;
             }
 

src/Symfony/Component/Dotenv/Tests/DotenvTest.php

@@ -154,4 +154,24 @@ public function testLoadDirectory()
         $dotenv = new Dotenv();
         $dotenv->load(__DIR__);
     }
+
+    public function testServerSuperglobalIsNotOverriden()
+    {
+        $originalValue = $_SERVER['argc'];
+
+        $dotenv = new DotEnv();
+        $dotenv->populate(array('argc' => 'new_value'));
+
+        $this->assertSame($originalValue, $_SERVER['argc']);
+    }
+
+    public function testEnvVarIsNotOverriden()
+    {
+        putenv('TEST_ENV_VAR=original_value');
+
+        $dotenv = new DotEnv();
+        $dotenv->populate(array('TEST_ENV_VAR' => 'new_value'));
+
+        $this->assertSame('original_value', getenv('TEST_ENV_VAR'));
+    }
 }