I was wondering if there is a way to compare old and new values in a validator within an entity prior to a flush.

I have a `Server` entity which renders to a form fine. The entity has a relationship to `status` (N->1) which, when the status is changed from `Unracked` to `Racked`, needs to check for SSH and FTP access to the server. If access is not achieved, the validator should fail.

I have mapped a validator callback to the method `isServerValid()` within the `Server` entity as described here
<http://symfony.com/doc/current/reference/constraints/Callback.html>. I can obviously access the 'new' values via `$this->status`, but how can I get the original value?

In pseudo code, something like this:

```
public function isAuthorValid(ExecutionContextInterface $context)
{
    $original = ... ; // get old values
    if( $this->status !== $original->status && $this->status === 'Racked' && $original->status === 'Unracked' )
    {
        // check ftp and ssh connection
        // $context->addViolationAt('status', 'Unable to connect etc etc');
    }
}

```

Thanks in advance!