Symfony2 simple voter example (credits: http://www.lexik.fr/blog/symfony/non-classe/faciliter-la-gestion-des-droits-dacces-avec-les-voters-2488)

ArticleController.php

<?php

namespace Foo\BarBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;

class ArticleController extends Controller
{
    public function editAction(Article article)
    {
        if (false === $securityContext->isGranted('ROLE_ARTICLE_EDIT', $article) {
            throw new AccessDeniedHttpException();
        }
        
        // Access granted
    }
}

OwnerVoter.php

<?php

namespace Foo\BarBundle\Security;

use Symfony\Component\Security\Core\Authorization\Voter\VoterInterface;
use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
 
class OwnerVoter implements VoterInterface
{
    public function supportsAttribute($attribute)
    {
        return 1 === preg_match('/^ROLE_ARTICLE_/', $attribute);
    }

    public function supportsClass($class) 
    {
        return true;
    }

    public function vote(TokenInterface $token, $object, array $attributes)
    {
        $vote = VoterInterface::ACCESS_ABSTAIN;

        foreach ($attributes as $attribute) {
            if (false === $this->supportsAttribute($attribute)) {
                continue;
            }
 
            $user = $token->getUser();
            $vote = VoterInterface::ACCESS_DENIED;
 
            // Check if the current user is the auhtor of the article
            if ($object->getAuthor()->getId() === $user->getId()) {
                $vote = VoterInterface::ACCESS_GRANTED;
            }
        }   

        return $vote;
    }
}

security.yml

# Administrators can edit any articles

security:
    role_hierarchy:
        ROLE_ADMIN:
            - ROLE_USER
            - ROLE_ARTICLE_EDIT

service.xml

<?xml version="1.0" ?>

<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <parameters>
        <parameter key="foo.bar.security.ownervoter.class">Foo\BarBundle\Security\OwnerVoter</parameter>
    </parameters>

    <services>
        <service id="foo.bar.security.ownervoter" class="%foo.bar.security.ownervoter.class%" public="false">
            <tag name="security.voter" />
        </service>
    </services>
</container>