Using column value as array index in doctrine

I got it: the trick here is use the INDEX BY word.

Query class

import the Query class (no always optional):

use \Doctrine\ORM\Query;

create the query:

$query = $this->data->em->createQuery('
    SELECT s 
    FROM models\Setting s 
    INDEX BY s.arg //to set array custom key
    WHERE s.category = :category');
$query->setParameter('category', 'general');

set the hidration mode in order to work with read-only arrays

$settings = $query->getResult(Query::HYDRATE_ARRAY); 

Display the value:

echo $settings['desc']['value'];  // prints "bar"

QueryBuilder

With the QueryBuilder object you can set the index at the from statement:

$qb = $em->createQueryBuilder();
$qb->select('s');
$qb->from('models\Settings', 's', 's.arg');  // here the magic
$result = $qb->getQuery()->getResult();

Then, you can access the object as:

$description = $result['desc'];
$value = $description->getValue();

FYI when using createQueryBuilder in your EntityRepository, you can directly specify the INDEX BY along with the alias:

$this->createQueryBuilder('p', 'p.id')

This avoids handling manually the from which is automatically handled in EntityRepositories.