Doctrine 2 postPersist then save/update entity - php

Question

I'm in the process of creating a trait that I want to insert into a number of my Doctrine entity classes. The trait basically allows for a slug property to be created using the Hashids PHP library based on the entities id (primary key).
I've included the required properties & getters/setters along with the postPersist() method on the trait, but I'm now wondering how I go about re-saving / updating / persisting that change from within the postPersist() method?
Any help or direction would be great.
SlugTrait
trait Slug
{
/**
* #ORM\Column(type="string")
*/
private $slug;
/**
* #ORM\PostPersist
*/
public function postPersist()
{
$this->slug = (new SlugCreator())->encode($this->id);
// Save/persist this newly created slug...?
}
public function getSlug()
{
return $this->slug;
}
public function setSlug($slug)
{
$this->slug = $slug;
}
}

Answer 1

After some trial and error I found out how to persist the update/change. As I'm using Laravel I just resolved the Entity Manager from the IoC container and then used that to persist the updated slug field like so (you could also just new up the Entity Manager manually):
trait Slug
{
/**
* #ORM\Column(type="string")
*/
protected $slug;
/**
* #ORM\PostPersist
*/
public function postPersist()
{
$this->slug = (new SlugCreator())->encode($this->id);
// Save/persist this newly created slug.
// Note: We must add the top level class annotation
// '#ORM\HasLifecycleCallbacks()' to any Entity that
// uses this trait.
$entityManager = App::make('Doctrine\ORM\EntityManagerInterface'); // or new up the em "new EntityManager(...);
$entityManager->persist($this);
$entityManager->flush();
}
public function getSlug()
{
return $this->slug;
}
public function setSlug($slug)
{
$this->slug = $slug;
}
}