symfony2 doctrine findBy id in arrayCollection - php

Question

Using Symfony2.3.4 and Doctrine.
I have a class Student with a ManyToMany relation with a class Edition.
Now in my StudentController I have this IndexAction($edition_id) to list not all students in the DB but only those related to the given Edition id.
$entities = $em->getRepository('PersonBundle:Student')->findBy(array(
????????
));
I'm thinking of some kind of criteria to use with $edition_id but can't come up with any.
Tips appreciated, thanks.
#dmnptr:
I'm trying that, I'm quite new to this so tell me if I did something wrong.
I put that function you wrote in the controller and in the method IndexAction($edition) I added
$students = this->findAllByEdition($edition);
now the problem is that the parameter $edition is coming from a twig template like this:
<a href="{{ path('student', { 'edition': entity}) }}"</a>
being entity who holds the Edition object.
But when I do it like this entity returns the __toString() method, meaning a string with the name of the edition, not the edition itself which is what the function you gave me uses.
Now, do you happen to know a way to get the object itself from the template, not the __toString() method, thanks...

Answer 1

You should use custom repository method. Pass $edition as a parameter, not just an id. Something like this:
public function findAllByEdition($edition)
{
$em = $this->getEntityManager();
$queryText = "SELECT s FROM PersonBundle:Student s ";
$queryText .= "WHERE :edition MEMBER OF s.editions";
$query = $em->createQuery($queryText);
$query->setParameter('edition', $edition)
return $query->getResult();
}