Ошибка при формировании предварительного запроса

$category = trim($_POST["spend_category"]);
        $cost = $_POST["cost"];
 
        $statement = $mysqli->prepare("SELECT id FROM cost_categories WHERE name = ?");
        $statement->bind_param("s", $category);
        $statement->execute();
        $statement->bind_result($category_id);
        $statement->fetch();
 
        if(empty($category_id)){
            echo "Error occured! Cant find category '" . $category . "'<br>";
        }
 
        if(!is_numeric($cost)){
            echo "Error occured! 'Cost' value must be number, cost = " . $cost . "<br>";
        } else {
            $cost = intval($cost);
            $statement = $mysqli->prepare("INSERT INTO costs (category,amount) VALUES (?,?)");
            
            $statement->bind_param("ii", $category_id, $cost);
            $statement->execute();
 
        }

$mysqli->prepare("INSERT INTO costs (category,amount) VALUES (?,?)");

var_dump($statement = $mysqli->prepare("SELECT id FROM cost_categories WHERE name = ?"));
..
if(!$statement->execute())
    var_dump($statement->error);

$statement->bind_param("ii", intval($category_id), $cost);