预处理查询及结果绑定处理
http://www.imooc.com/wenda/detail/576281
https://www.php.net/manual/en/mysqli-stmt.get-result.php
https://www.php.net/manual/en/mysqli-stmt.bind-result.php
$stmt->store_result(); $stmt->num_rows; 这句好像得搭配上句才可以使用
$mysqli_stmt -> bind_result() 绑定结果集中值到变量
$mysqli_stmt -> fetch() 遍历结果集
bind_result() 绑定结果集中的值到变量
mysqli prepare bind_param bind_result $stmt->free_result(); $stmt->close(); $conn->close();
mysqli prepare bind_param bind_result