Select subset of properties from Doctrine entity for serialization - serialization

Question

I am building a webservice that transmits json representations of domain models over a websocket connection. The entities are mapped with Doctrine, which unfortunately restricts me to only using protected or private properties in my entity classes. In order to include private properties in the json, I have been using this trait across my entities:
/**
* A trait enabling serialization for Doctrine entities for websocket transports.
* Unfortunately, this cannot be included in the abstract class for Doctrine entities
* as the parent class is unable to access private properties enforced by Doctrine.
*/
trait SerializableTrait
{
/**
* Implements {#link \JsonSerializable} interface.
* #return string - json representation
*/
public function jsonSerialize()
{
return get_object_vars($this);
}
}
However, the objects received on the client side should only contain a subset of the entity's properties to reduce load on the websocket connection and prevent sniffing of private information. Could this be realized elegantly in php without using the Reflection API or subclassing from a base class for client objects (i don't really want to split the entity class). Or is there maybe a way to use public properties in Doctrine entities that I am unware of? I am looking for something alone the lines of
$lightweightEntity = EntityStripper::strip($entity);
Thanks in advance!

Answer 1

Although initially not keen on using the Reflection API, it seems to be the only viable solution. So I came up with this solution parsing a custom #Serializable annotation to determine which properties are serialized:
use Doctrine\Common\Annotations\AnnotationReader;
use App\Model\Annotations\Serializable;
/**
* A trait enabling serialization of Doctrine entities for websocket transports.
*/
trait SerializableTrait
{
/**
* Implements {#link \JsonSerializable} interface and serializes all
* properties annotated with {#link Serializable}.
* #return string - json representation
*/
public function jsonSerialize()
{
// Circumvent Doctrine's restriction to protected properties
$reflection = new \ReflectionClass(get_class($this));
$properties = array_keys($reflection->getdefaultProperties());
$reader = new AnnotationReader();
$serialize = array();
foreach ($properties as $key) {
// Parse annotations
$property = new \ReflectionProperty(get_class($this), $key);
$annotation = $reader->getPropertyAnnotation($property, get_class(new Serializable()));
// Only serialize properties with annotation
if ($annotation) {
$serialize[$key] = $this->$key;
}
}
return json_encode($serialize, JSON_FORCE_OBJECT);
}
}