Warning: mysqli_stmt::bind_param(): Number of variables doesn't match number of parameters in prepared statement am i wrong?

Question

     public function createBarang($nama_barang, $harga_satuan, $stok){
            $stmt = $this->con->prepare("INSERT INTO `barang` (`id_barang`, `nama_barang`, `harga_satuan`, `stok`) VALUES (NULL, '?', '?', '?');");
            $stmt->bind_param("sii",$nama_barang, $harga_satuan, $stok);

            if($stmt->execute()){
                return true;
            }else{
                return false;
            }

        }

is already sent to database but the value is "?" because variable dont match with parameters

is anything wrong with my code?

screenshoot database

Answer 1

set id_barang autoincrement in mysql, second step don't use '?' but only ? like:

    public function createBarang($nama_barang, $harga_satuan, $stok){
    $stmt = $this->con->prepare("INSERT INTO `barang` (`nama_barang`, 
    `harga_satuan`, `stok`) VALUES (?, ?, ?);");
    $stmt->bind_param("sii",$nama_barang, $harga_satuan, $stok);

    if($stmt->execute()){
        return true;
    }else{
        return false;
    }

}