Doctrine2 ORM does not save changes to a DateTime field - oop

Question

I have a User entity:
use Doctrine\ORM\Mapping as ORM;
/**
* ExampleBundle\Entity\User
*
* #ORM\Entity()
*/
class User
{
// ...
/**
* #ORM\Column(type="service_expires_at", type="date", nullable=true)
*/
private $service_expires_at;
public function getServiceExpiresAt()
{
return $this->service_expires_at;
}
public function setServiceExpiresAt(\DateTime $service_expires_at)
{
$this->service_expires_at = $service_expires_at;
}
}
When i update the User's service_expires_at as following, the updated service_expires_at value is NOT saved back into the database:
$date = $user->getServiceExpiresAt();
var_dump($date->format('Y-m-d')); // 2013-03-08
$date->modify('+10 days');
var_dump($date->format('Y-m-d')); // 2013-03-18
$user->setServiceExpiresAt($date);
$em->persist($user);
$em->flush();
However if i pass a new DateTime object to service_expires_at, the updated value is saved correctly:
$date = $user->getServiceExpiresAt();
$date->modify('+10 days');
$user->setServiceExpiresAt(new \DateTime($date->format('Y-m-d'));
$em->persist($user);
$em->flush();
Why is this happening?

Answer 1

The DateTime instances returned by ExampleBundle\Entity\User#getServiceExpiresAt() are the same objects stored in the entity itself, which breaks encapsulation.
The UnitOfWork in Doctrine ORM applies strict comparison for changesets, which basically means that in the case of properties of entities containing objects, if the object instance hasn't changed, the ORM does not detect a change.
In strict comparison, following is true:
$dateTime1 = new \DateTime('#0');
$dateTime2 = new \DateTime('#0');
$dateTime3 = $dateTime1;
var_dump($dateTime1 !== $dateTime2); // true
var_dump($dateTime1 === $dateTime3); // true
$dateTime1->modify('+1 day');
var_dump($dateTime1 === $dateTime3); // true
This is a very common mistake among newcomers in OOP programming, and it can be solved quickly by fixing your getters and setters so that the original instance is never shared outside of your object, like in following example:
public function getServiceExpiresAt()
{
return clone $this->service_expires_at;
}
public function setServiceExpiresAt(\DateTime $service_expires_at)
{
$this->service_expires_at = clone $service_expires_at;
}
This will also fix your problem with Doctrine ORM.
Also, please note that this fixes possible leaks in your logic. For example, following code is buggy and hard to debug (when applying your currently broken getters/setters):
$bankTransaction1 = $someService->getTransaction(1);
$bankTransaction2 = $someService->getTransaction(2);
// leak! Now both objects reference the same DateTime instance!
$bankTransaction2->setDateTime($bankTransaction1->getDateTime());
// bug! now both your objects were modified!
$bankTransaction1->getDateTime()->modify('+1 day');
So, regardless of the ORM part in the question, please don't break encapsulation.

Answer 2

Consider using DateTimeImmutable class for your date/time properties. Thereby, note that DateTimeImmutable is not an instance of DateTime.

Answer 3

I have exactly the same problem when i am trying to insert an entity with a past date (i'm trying to migrate an old database to new schema with it's data too).
I tried to clone the object in both setter and getter and it's useless. Doctrine 2 saves the current date. Checked the schema, the field is date time not time stamp and default is null.
How can this be?
EDIT:
please excuse my lack of attention, my colleague dev added a prePersist event:
/**
* #ORM\PrePersist
*/
function onPrePersist() {
$this->created_at = new \DateTime('now');
}