How to get a one-dimensional scalar array as a doctrine dql query result?

Question

I want to get an array of values from the id column of the Auction table. If this was a raw SQL I would write:

SELECT id FROM auction

But when I do this in Doctrine and execute:

$em->createQuery("SELECT a.id FROM Auction a")->getScalarResult(); 

I get an array like this:

array(
    array('id' => 1),
    array('id' => 2),
)

Instead, i'd like to get an array like this:

array(
    1,
    2
)

How can I do that using Doctrine?

Answer 1

PHP < 5.5

You can use array_map, and since you only have on item per array, you can elegantly use 'current' as callback, instead of writing a closure.

$result = $em->createQuery("SELECT a.id FROM Auction a")->getScalarResult();
$ids = array_map('current', $result);

See Petr Sobotka's answer below for additional info regarding memory usage.

PHP >= 5.5

As jcbwlkr's answered below, the recommended way it to use array_column.

Answer 2

As of PHP 5.5 you can use array_column to solve this

$result = $em->createQuery("SELECT a.id FROM Auction a")->getScalarResult();
$ids = array_column($result, "id");

Answer 3

A better solution is to use PDO:FETCH_COLUMN . To do so you need a custom hydrator:

//MyProject/Hydrators/ColumnHydrator.php
namespace DoctrineExtensions\Hydrators\Mysql;

use Doctrine\ORM\Internal\Hydration\AbstractHydrator, PDO;

class ColumnHydrator extends AbstractHydrator
{
    protected function hydrateAllData()
    {
        return $this->_stmt->fetchAll(PDO::FETCH_COLUMN);
    }
}

Add it to Doctrine:

$em->getConfiguration()->addCustomHydrationMode('COLUMN_HYDRATOR', 'MyProject\Hydrators\ColumnHydrator');

And you can use it like this:

$em->createQuery("SELECT a.id FROM Auction a")->getResult("COLUMN_HYDRATOR");

More info: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/dql-doctrine-query-language.html#custom-hydration-modes