On Taming Repository Classes in Doctrine… Among other things.

criteria.php

interface Specification
{
    public function getCriteria();
}

class FilterGroup implements Specification
{
    private $group;

    public function __construct($group)
    {
        $this->group = $group;
    }

    public function getCriteria()
    {
        return new Expr\Comparison('group', Expr\Comparison::EQ, new Expr\Value($this->group));
    }
}

$specification = Criteria::create();
$specification->where(
    $specification->expr()->andX(
        (new Spec\FilterGroup($groupId))->getCriteria(),
        (new Spec\FilterPermission($permission))->getCriteria()
    )
);

$groups = $app['orm.ems']['api']
    ->getRepository('\EasyBib\Api\Entity\Group')
    ->matching($specification);

rulerz.php

$rulerz = new RulerZ(/* stuff */);

// 1. Write a rule.
$rule  = 'group in :groups and points > :points and length(name) > 2';

// 2. Filter a QueryBuilder
$usersQb = $entityManager
    ->createQueryBuilder()
    ->select('u')
    ->from('Entity\User', 'u');

// or an array of objects
$usersObj = [
    new User('Joe', 'guest', 40),
    new User('Moe', 'guest', 20),
];

// 3. Enjoy!
$parameters = [
    'points' => 30,
    'groups' => ['customer', 'guest'],
];

var_dump($rulerz->filter($usersQb, $rule, $parameters));
var_dump($rulerz->filter($usersObj, $rule, $parameters));

rulerz_specification.php

interface Specification
{
    public function getRule();
    public function getParameters();
}   

class FilterGroup implements Specification
{   
    private $group;
    
    public function __construct($group)
    {   
        $this->group = $group;
    }
    
    public function getRule()
    {
        return 'group = :group';
    }
    
    public function getParameters()
    {   
        return [
            'group' => $this->group,
        ];
    } 
}

class AndX implements Specification
{
    private $specifications = [];

    public function __construct(array $specifications = [])
    {
        foreach ($specifications as $specification) {
            $this->specifications[] = $specification;
        }
    }
        
    public function getRule()
    {   
        return implode(' AND ', array_map(function ($specification) {
            return $specification->getRule();
        }, $this->specifications));
    }   
        
    public function getParameters()
    {
        return call_user_func_array('array_merge', array_map(function ($specification) {
            return $specification->getParameters();
        }, $this->specifications));
    }   
}

$specification = new Spec\AndX(
    new Spec\FilterGroup($groupId),
    new Spec\FilterPermission($permission)
);

$rulerz->filter($target, $specification->getRule(), $specification->getParameters());

specifications.php

interface Specification
{
    public function match(QueryBuilder $qb, $dqlAlias);
    public function modifyQuery(Query $query);
}

class FilterGroup implements Specification
{
    private $group;

    public function __construct($group)
    {
        $this->group = $group;
    }

    public function match(QueryBuilder $qb, $dqlAlias)
    {
        $qb->setParameter('group', $this->group);

        return $qb->expr()->eq($dqlAlias . '.group', ':group');
    }

    public function modifyQuery(Query $query) { /* empty ***/ }
}

$specification = new Spec\AsArray(new Spec\AndX(
    new Spec\FilterGroup($groupId),
    new Spec\FilterPermission($permission)
));

$groups = $app['orm.ems']['api']
    ->getRepository('\EasyBib\Api\Entity\Group')
    ->match($specification);