PHP - Selecting A Name From Table 2 But Get No Returns

Me again.. I'm fetching data from MySQL but each person in people.php is displayed two times instead one.. The issue must be inside models_category_tbl table, because each person have more then one result. Any advice is appreciated. What should I do?

I would like to display people something like that:

1 John Doe 1 IT developer, 3 mechanic

models/model = person

category = occupation/skills

MySQL:

model_index table
+---------+------------+-------------+-------------------+---------------+----------------+
|model_id | model_name | model_title | model_description | model_country | model_slug	  |
+---------+------------+-------------+-------------------+---------------+----------------+
| 1 	  | John Doe   | Johns title | Johns desc        | Hungary       | john-doe 	  |	
+---------+------------+-------------+-------------------+---------------+----------------+

models_category_tbl table
+-------------+---------------------+---------------------+
| category_id | model_category_name | model_category_slug |
+-------------+---------------------+---------------------+
| 1           | it developer        | it-developer        |
| 2           | photographer	    | photographer        |
| 3           | mechanic            | mechanic            |
+-------------+---------------------+---------------------+

models_category_ids table
+----+----------+-------------+
| id | model_id | category_id |
| 1  | 1        | 1           | 
| 1  | 1        | 3           |
+----+----------+-------------+

PHP function to fecth data:

        public function getAllModels1 () {

        $sql = "SELECT * FROM models_index  JOIN models_category_ids ON models_index.model_id=models_category_ids.model_id JOIN models_category_tbl ON  models_category_tbl.category_id=models_category_ids.category_id" ;
            $stmt = $this->conn->prepare($sql);
            $stmt->execute();
            $result = $stmt->fetchAll((PDO::FETCH_OBJ));
            
            return $result;            
    }

people.php

<?php 
declare(strict_types=1);
ob_start();
include "includes/connect.php";
include "includes/functions.php";
 

   	$model = new ModelsData();
	$models = $model->getAllModels1();


	foreach ($models as $model) { ?> 


	<a href="model.php?id=<?= $model->model_id ?>"><img src="<?= $model->model_img_path ?><?=$model->model_img_name ?>"></a>	 
 
	<?php echo $model->model_id . " " .  $model->model_name . " " . $model->category_id .  " " . $model->model_category_name  ; ?>
	

	<h3><?= $model->model_name ?></h3>

 
<?php }  ?>

Output:

 1 John Doe 1 IT developer 
 1 John Doe 3 mechanic

Hi, I am trying to expand my very limited PHP by building a CMS. It's all new to me so please be courteous with your replies ?

I little history of my problem.

I am running xampp on a windows 10 running php 5.6.38

I have taken two video courses and on each I got stumped halfway through with a very similar problem.
The first was using mysql which I was converting to mysqli until I run into a problem.
I then started a new course which used mysqli but it was from 2014 so not sure which version of PHP or if it would even matter.

I am copying everything word for word and even downloaded the course file on the first one and still got the same problem so I'm wondering if there is something wrong with my setup - config?.

The problem.
I am trying to pull data from the database using a while loop. Each time it returns NULL.

This is the code:
 

<?php 

error_reporting(E_ALL);
ini_set('display_errors',1);

include("includes/database.php");
include("includes/header.php");

if ($connection) {        
    echo "Great, we're connected to the database<br><br>";
    }else {
        echo "Bummer, it didn't connect to the database!";
        }

     $query = "SELECT * FROM categories";
   $result_set = mysqli_query($connection, $query) ;

   if (!$result_set) {
           die("Query Failed".msqli_error($connection));
               }

   while ($row = mysqli_fetch_array($result_set)) {
               echo $row['cat_title'];
               }

    var_dump($result_set);                      
        
 ?>

This is the response:

Great, we're connected to the database

object(mysqli_result)#3 (5) { ["current_field"]=> int(0) ["field_count"]=> int(2) ["lengths"]=> NULL ["num_rows"]=> int(0) ["type"]=> int(0) }

Question:
the database table (categories) is populated with two rows (id & cat_title) and there is data in there.
So why does it not retrieve the data?

Thanks for your help.