bug #22183 [Process] Fix bug which wiped or mangled env vars (pjcdawk…

…ins)

This PR was squashed before being merged into the 3.2 branch (closes #22183).

Discussion
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[Process] Fix bug which wiped or mangled env vars

| Q             | A
| ------------- | ---
| Branch?       | 3.2
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | N/A

Fixing (and testing) a one-character bug introduced in a recent commit symfony/process@7d21c4a

Commits
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9439237 [Process] Fix bug which wiped or mangled env vars

src/Symfony/Component/Process/Process.php

@@ -277,7 +277,7 @@ public function start(callable $callback = null)
             }
 
             foreach ($env as $k => $v) {
-                $envBackup[$k] = getenv($v);
+                $envBackup[$k] = getenv($k);
                 putenv(false === $v || null === $v ? $k : "$k=$v");
             }
             $env = null;

src/Symfony/Component/Process/Tests/ProcessTest.php

@@ -1403,6 +1403,20 @@ public function testSetBadEnv()
         $this->assertSame('', $process->getErrorOutput());
     }
 
+    public function testEnvBackupDoesNotDeleteExistingVars()
+    {
+        putenv('existing_var=foo');
+        $process = $this->getProcess('php -r "echo getenv(\'new_test_var\');"');
+        $process->setEnv(array('existing_var' => 'bar', 'new_test_var' => 'foo'));
+        $process->inheritEnvironmentVariables();
+
+        $process->run();
+
+        $this->assertSame('foo', $process->getOutput());
+        $this->assertSame('foo', getenv('existing_var'));
+        $this->assertFalse(getenv('new_test_var'));
+    }
+
     public function testInheritEnvEnabled()
     {
         $process = $this->getProcess(self::$phpBin.' -r '.escapeshellarg('echo serialize($_SERVER);'), null, array('BAR' => 'BAZ'));