symfony · fabpot · Mar 31, 2014 · Feb 12, 2014 · Feb 17, 2014 · Feb 17, 2014
diff --git a/UPGRADE-2.5.md b/UPGRADE-2.5.md
@@ -56,10 +56,11 @@ Validator
 
    After:
 
-   Default email validation is now done via a simple regex which may cause invalid emails (not RFC compilant) to be 
+   Default email validation is now done via a simple regex which may cause invalid emails (not RFC compilant) to be
    valid. This is the default behaviour.
 
    Strict email validation has to be explicitly activated in the configuration file by adding
+
    ```
    framework:
       //...
@@ -68,7 +69,119 @@ Validator
       //...
 
    ```
+
    Also you have to add to your composer.json:
+
    ```
    "egulias/email-validator": "1.1.*"
    ```
+
+ * `ClassMetadata::getGroupSequence()` now returns `GroupSequence` instances
+   instead of an array. The sequence implements `\Traversable`, `\ArrayAccess`
+   and `\Countable`, so in most cases you should be fine. If you however use the
+   sequence with PHP's `array_*()` functions, you should cast it to an array
+   first using `iterator_to_array()`:
+
+   Before:
+
+   ```
+   $sequence = $metadata->getGroupSequence();
+   $result = array_map($callback, $sequence);
+   ```
+
+   After:
+
+   ```
+   $sequence = iterator_to_array($metadata->getGroupSequence());
+   $result = array_map($callback, $sequence);
+   ```
+
+ * The array type hint in `ClassMetadata::setGroupSequence()` was removed. If
+   you overwrite this method, make sure to remove the type hint as well. The
+   method should now accept `GroupSequence` instances just as well as arrays.
+
+   Before:
+
+   ```
+   public function setGroupSequence(array $groups)
+   {
+       // ...
+   }
+   ```
+
+   After:
+
+   ```
+   public function setGroupSequence($groupSequence)
+   {
+       // ...
+   }
+   ```
+
+ * The validation engine in `Symfony\Component\Validator\Validator` was replaced
+   by a new one in `Symfony\Component\Validator\Validator\RecursiveValidator`.
+   With that change, several classes were deprecated that will be removed in
+   Symfony 3.0. Also, the API of the validator was slightly changed. More
+   details about that can be found in UPGRADE-3.0.
+
+   You can choose the desired API via the new "api" entry in
+   app/config/config.yml:
+
+   ```
+   framework:
+       validation:
+           enabled: true
+           api: auto
+   ```
+
+   When running PHP 5.3.9 or higher, Symfony will then use an implementation
+   that supports both the old API and the new one:
+
+   ```
+   framework:
+       validation:
+           enabled: true
+           api: 2.5-bc
+   ```
+
+   When running PHP lower than 5.3.9, that compatibility layer is not supported.
+   On those versions, the old implementation will be used instead:
+
+   ```
+   framework:
+       validation:
+           enabled: true
+           api: 2.4
+   ```
+
+   If you develop a new application that doesn't rely on the old API, you can
+   also set the API to 2.5. In that case, the backwards compatibility layer
+   will not be activated:
+
+   ```
+   framework:
+       validation:
+           enabled: true
+           api: 2.5
+   ```
+
+   When using the validator outside of the Symfony full-stack framework, the
+   desired API can be selected using `setApiVersion()` on the validator builder:
+
+   ```
+   // Previous implementation
+   $validator = Validation::createValidatorBuilder()
+       ->setApiVersion(Validation::API_VERSION_2_4)
+       ->getValidator();
+
+   // New implementation with backwards compatibility support
+   $validator = Validation::createValidatorBuilder()
+       ->setApiVersion(Validation::API_VERSION_2_5_BC)
+       ->getValidator();
+
+   // New implementation without backwards compatibility support
+   $validator = Validation::createValidatorBuilder()
+       ->setApiVersion(Validation::API_VERSION_2_5)
+       ->getValidator();
+   ```
+