$fields = M('fields') -> select();
    $aa = json_encode($fields);
    $bb = json_decode($aa);
    
    $bb -> 0;//获取不到任何数据，应该怎么写呢
    
    print_r($bb);
    结果为：

Array
(

[0] => stdClass Object
    (
        [fields_id] => 1
        [name] => 勘探
    )

[1] => stdClass Object
    (
        [fields_id] => 2
        [name] => 钻完井
    )

[2] => stdClass Object
    (
        [fields_id] => 3
        [name] => 采油采气
    )

[3] => stdClass Object
    (
        [fields_id] => 4
        [name] => 油气储运
    )

[4] => stdClass Object
    (
        [fields_id] => 5
        [name] => 地面工程
    )

[5] => stdClass Object
    (
        [fields_id] => 6
        [name] => 销售炼化
    )

[6] => stdClass Object
    (
        [fields_id] => 7
        [name] => 新能源
    )

[7] => stdClass Object
    (
        [fields_id] => 8
        [name] => 综合
    )

)

里面的数据怎么取啊？求写法。比如要取[0]下面所有的数据怎么写？要是取[0]
下面的[name]又怎么写呢？