bug symfony#15243 Reload the session after regenerating its id (jakzal)

This PR was merged into the 2.3 branch.

Discussion
----------

Reload the session after regenerating its id

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#15033
| License       | MIT
| Doc PR        | -

This is a fix preventing [a PHP bug](https://bugs.php.net/bug.php?id=70013), which I'm not sure when or IF is going to be fixed.

Commits
-------

99b9c78 [HttpFoundation] Reload the session after regenerating its id
eda5cb1 [HttpFoundation] Add a test case to confirm a bug in session migration

Author: fabpot

src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php

@@ -203,7 +203,13 @@ public function regenerate($destroy = false, $lifetime = null)
             $this->metadataBag->stampNew();
         }
 
-        return session_regenerate_id($destroy);
+        $isRegenerated = session_regenerate_id($destroy);
+
+        // The reference to $_SESSION in session bags is lost in PHP7 and we need to re-create it.
+        // @see https://bugs.php.net/bug.php?id=70013
+        $this->loadSession();
+
+        return $isRegenerated;
     }
 
     /**

src/Symfony/Component/HttpFoundation/Tests/Session/Storage/NativeSessionStorageTest.php

@@ -119,6 +119,17 @@ public function testRegenerateDestroy()
         $this->assertEquals(11, $storage->getBag('attributes')->get('legs'));
     }
 
+    public function testSessionGlobalIsUpToDateAfterIdRegeneration()
+    {
+        $storage = $this->getStorage();
+        $storage->start();
+        $storage->getBag('attributes')->set('lucky', 7);
+        $storage->regenerate();
+        $storage->getBag('attributes')->set('lucky', 42);
+
+        $this->assertEquals(42, $_SESSION['_sf2_attributes']['lucky']);
+    }
+
     public function testDefaultSessionCacheLimiter()
     {
         $this->iniSet('session.cache_limiter', 'nocache');