PHP and Doctrine: how to create unique IDs

Question

I'd like to create unique IDs, something like dujUSJue9389sjgjik.

I've used the Doctrine's UUID strategy to create them, but the result is something like d9c363ae-a1b7-11e6-a66d-9e9923e30d94: I don't like the use of dashes and also I'd like to have shorter IDs.

They have to identify some entities to build an URL like http://example.com/entity/hduicw43tv43bic.

Using PHP's uniqid() doesn't guarantee the uniqueness of the generated value. I think a conflict is very rare, but, anyway, not excluded at all, so I'm not considering it "secure" (a conflict may cause an exception and the rows creation may cause a lot of headache to fix).

So, using Doctrine and Symfony, I'm looking for a way to generate a value like ajybUYBD74883bj8d74NJ and check for its uniqueness. If it is already present, a new value has to be generated. Once the entity has a unique value, it can be persisted. The generation should happen when the entity is created.

Any ideas on how to implement this?

There's no real unique value generation algorithm that guarantees uniqueness, including UUID/GUID. — Jakub Matczak, Nov 03 '16 at 11:46
Yes, I'm aware of this. For this I'm looking for a procedure to check the uniqueness and on fail (the generated ID already exists) regenerate it. This should be done in Doctrine entity itself. — Aerendir, Nov 03 '16 at 11:47
This should be done in entity itself. It's not entity's job to check other entities (inclufing calling repository). It should be ID generator's job. You can try to create a custom ID generator, but I can't find documentation about it. Anyway here's an example in psylosss's answer: http://stackoverflow.com/questions/15039665/generate-unique-id-doctrine-symfony2 — Jakub Matczak, Nov 03 '16 at 11:52
UUID is just a number. You can display it as hexadecimal text with inserted hyphen characters, but it's still a 128-bit value. You can represent it as you want (e.g: base64-encoded) — Federkun, Nov 03 '16 at 11:54
@Federkun, yes, for sure, but I don't want it be too much long... Maybe UUID has a technical meaning, but I'm intending it simply as a unique value to identify an entity, without constraints on length, format or anything else. Its unique property, for the purpose of this question, is its uniqueness. — Aerendir, Nov 03 '16 at 11:57

score 4 · Accepted Answer · edited May 23 '17 at 12:10

So, mixing the answer by @Matteo and the answer by psyloss suggested by @Jakub Matczak I came up with this:

class Company
{
    /**
     * @var string
     *
     * @ORM\Column(name="id", type="string")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="CUSTOM")
     * @ORM\CustomIdGenerator(class="AppBundle\Doctrine\IdGenerator")
     */
     private $id;

     ...

and then

namespace AppBundle\Doctrine;

use Doctrine\ORM\EntityManager;
use Doctrine\ORM\Id\AbstractIdGenerator;
use Ramsey\Uuid\Uuid;

/**
 * {@inheritdoc}
 */
class IdGenerator extends AbstractIdGenerator
{
    /**
     * {@inheritdoc}
     */
    public function generate(EntityManager $em, $entity)
    {
        $uuid = Uuid::uuid4()->getHex();

        if (null !== $em->getRepository(get_class($entity))->findOneBy(['id' => $uuid])) {
            $uuid = $this->generate($em, $entity);
        }

        return $uuid;
    }
}

This generator also checks for an existing entity with the same name, regenerating the UUID if required and guaranteeing the uniqueness.

The generated value is exactly what I want: 7b165049eb224f548021f68caefc57f6.

score 1 · Answer 2 · answered Nov 03 '16 at 11:56

1

If Doctrine's UUID strategy is good you can simply transform that:

$in = 'd9c363ae-a1b7-11e6-a66d-9e9923e30d94';
$out = base_convert(strtr($in,'-',''),16,36);
print_r($out);

short, no dash, reverseable

answered Nov 03 '16 at 11:56

cske

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score 1 · Answer 3 · answered Nov 03 '16 at 13:02

I suggest you to use the ramsey-uuid library, ad Use As Follow:

$uuid = \Ramsey\Uuid\Uuid::uuid4();
echo $uuid->getHex();

Alternately, if you already have a UUID, you may do this:

$uuid = \Ramsey\Uuid\Uuid::fromString('f6a1fd62-1445-42fc-9e7b-d8c6e9da33a1');
echo $uuid->getHex();

PHP and Doctrine: how to create unique IDs

4 Answers4

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