minor symfony#10594 Fixes var name in callback (mauricesvay)

This PR was merged into the master branch.

Discussion
----------

Fixes var name in callback

<!--

If your pull request fixes a BUG, use the oldest maintained branch that contains
the bug (see https://symfony.com/roadmap for the list of maintained branches).

If your pull request documents a NEW FEATURE, use the same Symfony branch where
the feature was introduced (and `master` for features of unreleased versions).

-->

Commits
-------

48b1fec Fixes var name in callback

Author: javiereguiluz

components/serializer.rst

@@ -629,7 +629,7 @@ When serializing, you can set a callback to format a specific object property::
 
     // all callback parameters are optional (you can omit the ones you don't use)
     $callback = function ($innerObject, $outerObject, string $attributeName, string $format = null, array $context = array()) {
-        return $dateTime instanceof \DateTime ? $dateTime->format(\DateTime::ISO8601) : '';
+        return $innerObject instanceof \DateTime ? $innerObject->format(\DateTime::ISO8601) : '';
     };
 
     $normalizer->setCallbacks(array('createdAt' => $callback));