Query a fixed number of random questions in Symfony/Doctrine - php

Question

I'm working on website for multiple choice questions where I use symfony. The thought is to have a very big question database that categorized by topic. And then a test 1 - n chapterSelections. Each chapterSelections should contain a chapterID and a number. The number decides how many random questions it should pick from that chapter.
In the chapter entity it has a getQuestions function, and in the quetions entity, it has an getAlternatives functions.
BUT, I need a function in the chapterSelections entity that says, getRandomQuestions(int n)???
In my view, I was thinking of something like:
{% block body %}
<!-- Main component for a primary marketing message or call to action -->
<div class="jumbotron">
<h1>Welcome</h1>
<h1>{{ test.name }}</h1>
{% for c in test.chapterSelections %}
<h1>Chapter: {{ c.getChapterID() }} - {{ c.numberOfQuestions }}</h1>
{% for q in c.randomQuestions %}
<h3>{{ q.questionText}} </h3>
{% for a in q.alternatives %}
<p> {{a.alternativeText }} </p>
{% endfor %}
{% endfor %}
{% endfor %}
</div>
{% endblock %}
I know I'm still missing the formcontrols like radiobuttons and formgroups, but this is the hardest part. I need a way to access a number of random questions from the chapterSelection entity. Any thoughts? Some info that is helpful that I have left out?
EDIT
This is how i use getQuestions in my chapter entity:
Entity/chapter.php
use Doctrine\Common\Collections\ArrayCollection;
/**
* #ORM\OneToMany(targetEntity="question", mappedBy="chapterID", cascade={"persist", "remove"}, orphanRemoval=true)
*/
protected $questions;
public function __construct()
{
$this->questions= new ArrayCollection();
}
public function getQuestions()
{
return $this->questions;
}
But I want this functionality in my chapterSelection, with random selection and a specified (in each chapterSelection record) number of questions.