PHP的回声JSON在foreach循环

    $product_ids = explode(',', $product_ids);    $product_ids = array_filter($product_ids);    $final_data = array();    foreach ($product_ids as $key => $product_id) {          $sth = $this->db->prepare("SELECt * FROM products Where id =:id ");          $sth->execute(array( ':id' => $product_id ));          $final_data[$product_id] = $sth->fetchAll();    }    echo json_enpre($final_data);