备份：关于mysqi的一些对比

mysqli->fetch_all 后面有三个参数，参数对比的返回结果如下：

MYSQLI_BOTH:

    [0] => Array

        (

            [0] => 1011

            [ID] => 1011

            [1] => Kudus

            [Name] => Kudus

            [2] => IDN

            [CountryCode] => IDN

            [3] => Central Java

            [District] => Central Java

            [4] => 95300

            [Population] => 95300

        )

MYSQLI_NUM:

    [0] => Array

        (

            [0] => 1011

            [1] => Kudus

            [2] => IDN

            [3] => Central Java

            [4] => 95300

        )

MYSQLI_ASSOC:

   [0] => Array

        (

            [ID] => 1011

            [Name] => Kudus

            [CountryCode] => IDN

            [District] => Central Java

            [Population] => 95300

        )

mysqli->fetch_array: 返回一条数组记录，可以带上面的参数；

fetch_assoc 返回的结果等同于 fetch_array（MYSQLI_ASSOC）; $row['name']

fetch_row 返回的结果等同于fetch_array(MYSQLI_NUM) $row[0]

fetch_field_direct 返回字段的元数据信息。例如长度，类型等等信息；

fetch_object 返回一个对象操作；前面都是在使用下标操作 $row->name;

如果查询不到数据：

fetch_all 返回的是一个数组对象；

tetch_object，fetch_row等返回的是NULL对象，这点是有很大的不同的;