PHP show data in checkbox

I am trying to retrieve data from the jokecategory table and place it within checkboxes. This is the SQL statement that I am using:

$sql = "SELECT joke.id, joke.joke_text, joke.joke_date, author.name, author.email, jokecategory.category_id
        FROM joke 
        INNER JOIN author ON joke.author_id = author.id
        INNER JOIN jokecategory ON joke.id = jokecategory.joke_id
        WHERE joke.id = :id";
$stmt = $dbConnection->prepare($sql);
$stmt->bindValue(':id', $id);
$stmt->execute();
$data = $stmt->fetch();
$joke_id = $data['id'];
$joke_text = $data['joke_text'];
$joke_date = $data['joke_date'];
$author_name = $data['name'];
$author_email = $data['email'];

This is what I have tried to retrieve the data:

<fieldset>
                <legend class="control-label">Categories:</legend>
                <?php foreach ($data['category_id'] as $checkbox) { ?>
                <div class="controls">      
                    <label for="category<?php echo($checkbox['id']);?>">
                    <input type="checkbox" name="categories[]" id="category<?php echo($checkbox['id']); ?>" value="<?php echo($checkbox['id']); ?>">
                    <?php echo($checkbox['name']); ?></label>
                </div>
                <?php } ?>
            </fieldset>

Unsure of how to echo the category_id's back out from the jokecategory table and place within checkboxes. Could someone kindly provide some assistance?