/** * {@inheritDoc} */ public function compareState(SnapshotInterface $snapshot) { $state = $snapshot->getState(); if (!is_array($state)) { throw new \UnexpectedValueException(__CLASS__ . ' can only handle array-serialized state'); } $objectState = (array) $snapshot->getObject(); $snapshotState = $snapshot->getState(); if ($objectState === $snapshotState) { return null; } return array_diff($objectState, $snapshotState); }