Вывод комментариев по id

$sql = mysqli_query($db, "select * from `comments` where `product_id`='".$_REQUEST['тут значение переменной переданой на страницу']."'");

<?=$data['prod']['id']?>

index.php?id=425

$id = (int) $_GET['id'];
$sql = mysqli_query($db, "select * from `comments` where `product_id`= $id");

$data['prod']['id'];

$id = $data['prod']['id'];
$sql = mysqli_query($db, "select * from `comments` where `product_id`= $id");

 public function view(){
        $params = App::getRouter()->getParams();
 
        if(isset($params[0])){
            $alias = strtolower($params[0]);
            $this->data['prod'] = $this->model->getbyAliasProd($alias);
 
 
        }
        if($_POST){
            if($this->model->add_comments($_POST)){
                Session::setFlash('Message sent!');
 
            }
 
        }
 
        $this->data['comments']= $this->model->getComments();
 
    }

$this->data['comments']= $this->model->getComments();

public function getComments(){
        $sql = "select * from comments where product_id=";
        return $this->db->query($sql);
    }

public function getComments($param){
        $sql = "select * from comments where product_id=$param";
        return $this->db->query($sql);
    }

$this->data['comments']= $this->model->getComments($this->data['prod']['id']);

<?php
 
class DB{
 
    protected $connection;
 
    public function __construct($host, $user, $password, $db_name){
        $this->connection = new mysqli($host, $user, $password, $db_name);
 
        if(mysqli_connect_error()){
            throw new Exception('Error connect to DB');
        }
    }
        public function query($sql){
            if(!$this->connection){
                return false;
            }
 
            $result = $this->connection->query($sql);
 
            if(mysqli_error($this->connection)){
                throw new Exception(mysql_error($this->connection));
            }
 
            if(is_bool($result)){
                return $result;
            }
 
            $data = array();
            while($row = mysqli_fetch_assoc($result)){
                $data[]= $row;
            }
            return $data;
        }
        public function escape($str){
            return mysqli_escape_string($this->connection, $str);
        }
 
 
}

            if(mysqli_error($this->connection)){
                throw new Exception(mysql_error($this->connection));
            }