Fatal error: Uncaught Error: Call to a member function execute()

Question

Ошибка Fatal error: Uncaught Error: Call to a member function execute() on boolean in C:\xampp\htdocs\connect7.php:22 Stack trace: 0 {main} thrown in C:\xampp\htdocs\connect7.php on line 22.

Подскажите в чем причина.

 ?php 
     define('DB_HOST', 'localhost');
     define('DB_USER', 'root');
     define('DB_PASS', '');
     define('DB_NAME', 'test');

     $conn = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_NAME);

     if (mysqli_connect_errno()) {
     echo "Failed to connect to MySQL: " . mysqli_connect_error();
     die();
     }

     $stmt = $conn->prepare("SELECT id, group, vk_za_rozkladom, vk_za_zaminoy, audut FROM zaminu;");

     $stmt->execute();

     $stmt->bind_result($id, $group, $vk_za_roz, $vk_za_zam, $audut);

     $products = array(); 

     while($stmt ->fetch()){
     $temp = array();
     $temp['id'] = $id; 
     $temp['group'] = $group; 
     $temp['vk_za_roz'] = $vk_za_roz; 
     $temp['vk_za_zam'] = $vk_za_zam; 
     $temp['audut'] = $audut;  
     array_push($products, $temp);
     }

     echo json_encode($products);