Doctrine ORM produce different output when using manual 'select' - doctrine-orm

Question

I'm a beginner with Doctrine ORM (v2.5.5) and Silex (v2.0.4)/Symfony (v3.1.6). I need to output my Date field to the YYYY-MM-DD format. Let's say I have this annotation and getter method on my Entity:
// src/App/Entity/Tnkb.php (simplified)
// 'expire' field
/**
* #ORM\Column(type="date")
*/
protected $expire;
// getter
public function getExpire()
{
return !is_object($this->expire) ? new \DateTime() : $this->expire->format('Y-m-d');
}
Here's my simplified controller for debugging purpose:
$app->get('/debug', function() use ($app) {
$tnkbRepo = $app['orm.em']->getRepository('\App\Entity\Tnkb');
$normalizer = new \Symfony\Component\Serializer\Normalizer\ObjectNormalizer();
$encoder = new \Symfony\Component\Serializer\Encoder\JsonEncoder();
$normalizer->setCircularReferenceHandler(function($obj){
return $obj->getId();
});
$serializer = new \Symfony\Component\Serializer\Serializer(array($normalizer), array($encoder));
$qb = $tnkbRepo->createQueryBuilder('c')
->setMaxResults(1);
//$query = $qb->getQuery(); // [1] <<-- this line produce proper YYYY-MM-DD format
//$query = $qb->select('c.expire')->getQuery(); // [2] <<-- this (manual select) line produce DateTime object.
$results = $query->getResult();
return $serializer->serialize($results, 'json');
});
With the first [1] line uncommented I got the proper output I wanted:
[more json output here]...,"expire":"1970-10-25",...
But with the second [2] line uncommented (I intendedly omitted other fields for testing) I got the following output, which wasn't what I expected:
[{"expire":{"timezone":{"name":"UTC","location":{"country_code":"??","latitude":0,"longitude":0,"comments":""}},"offset":0,"timestamp":25660800}}]
I also noticed, with the [2] line Doctrine seems to ignore my entity's getter method (I tried returning empty string). I expect the output will be the same as the [1] case, it makes me curious. My questions are:
How do I achieve the same proper YYYY-MM-DD format with the [2] version?
And why are they produce different output format?
Thank you.
UPDATE
More simplified /debug controller for testing (no serialization):
$app->get('/debug', function() use ($app) {
$tnkbRepo = $app['orm.em']->getRepository('\App\Entity\Tnkb');
$qb = $tnkbRepo->createQueryBuilder('c');
// [1a] normal query. doesn't return Entity, getExpire() isn't called.
/*$query = $qb->select('c.expire')
->setMaxResults(1)->getQuery();*/
// [2a] partial query. returns Entity, getExpire() called.
/*$query = $qb->select('partial c.{id,expire}')
->setMaxResults(1)->getQuery();*/
$results = $query->getResult();
var_dump($results);die;
});
Updated Entity method getExpire():
// src/App/Entity/Tnkb.php (simplified)
// 'expire' field
/**
* #ORM\Column(type="date")
*/
protected $expire;
protected $dateAsString = true;
protected $dateFormat = 'Y-m-d';
// getter
public function getExpire()
{
return ($this->expire instanceof \DateTime) ? $this->dateOutput($this->expire)
: $this->dateOutput(new \DateTime());
}
protected function dateOutput(\DateTime $date) {
if ($this->dateAsString) {
return $date->format($this->dateFormat);
}
return $date;
}
Controller dump results:
[1a] normal query:
// non-entity
array(1) { [0]=> array(1) { ["expire"]=> object(DateTime)#354 (3) { ["date"]=> string(26) "1970-10-25 00:00:00.000000" ["timezone_type"]=> int(3) ["timezone"]=> string(3) "UTC" } } }
[2a] partial object query:
// array of entity
array(1) { [0]=> object(App\Entity\Tnkb)#353 (23) { /* more properties */...["expire":protected]=> object(DateTime).../* more properties */
I found out this is normal behaviour with Doctrine, it has something to do with Partial Objects. See my comment below. Link: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/partial-objects.html

Answer 1

I don't think it's good practice to return a \DateTime sometimes but a formatted string other times. However maybe you have your reasons for doing this.
The only reason I can think of the difference in results is if Doctrine calls getters on the properties when loading an entity. I tested with a simple class which has the same expire property and getter. Returning the class still had the serialized (not formatted) \DateTime object, which would suggest that at some point your getter is being called and the property set to a new \DateTime.
My recommendation is to look at the DateTimeNormalizer provided by Symfony in 3.1. If you can't upgrade to 3.1 then you can easily build your own one. Then you can be sure you'll always have consistent \DateTime format in all your responses. You can all remove the ->format(...) from your getter then and always return a \DateTime object. I think this is a much cleaner approach.