json 大括号保存对象，为什么关联数组在json中表现为对象，用{}包裹关联数组的数据？

Question

实验数据：

//关联数组
$result_array1['msg'] = 13;
$result_array1['infor'] = 24;
//索引数组
$result_array2[] = 1;
$result_array2[] = 2;
//索引数组
$arr = array(0,1,3);
$arr[0] = $result_array1;
$arr[1] = $result_array2;
$arr[2] = $result_array1;
$arr[3] = 123;
$arr[4] = 3243;

$result_array['msg'] = 13;
$result_array['infor'] = 24;
$result_array['ra1'] = $arr;

var_dump($result_array);
var_dump(json_encode($result_array));

浏览器输出：

 array (size=3)
  'msg' => int 13
  'infor' => int 24
  'ra1' => 
    array (size=5)
      0 => 
        array (size=2)
          'msg' => int 13
          'infor' => int 24
      1 => 
        array (size=2)
          0 => int 1
          1 => int 2
      2 => 
        array (size=2)
          'msg' => int 13
          'infor' => int 24
      3 => int 123
      4 => int 3243
string '{"msg":13,"infor":24,"ra1":[{"msg":13,"infor":24},[1,2],{"msg":13,"infor":24},123,3243]}' (length=88)

补充：

//关联数组
$result_array1['msg'] = 13;
$result_array1['infor'] = 24;
//索引数组
$result_array2[] = 1;
$result_array2[] = 2;
//索引数组
$arr = array(0,1,3);
$arr[0] = $result_array1;
$arr[1] = $result_array2;
$arr[2] = $result_array1;
$arr[3] = 123;
$arr[4] = 3243;

$result_array[] = 13;
$result_array[] = 24;
$result_array[] = $arr;

var_dump($result_array);
var_dump(json_encode($result_array));

结果：

array (size=3)
  0 => int 13
  1 => int 24
  2 => 
    array (size=5)
      0 => 
        array (size=2)
          'msg' => int 13
          'infor' => int 24
      1 => 
        array (size=2)
          0 => int 1
          1 => int 2
      2 => 
        array (size=2)
          'msg' => int 13
          'infor' => int 24
      3 => int 123
      4 => int 3243
D:\wamp\www\test\array.php:47:string '[13,24,[{"msg":13,"infor":24},[1,2],{"msg":13,"infor":24},123,3243]]' (length=68)

实验结论：关联数组json表现为{}，索引数组表现为：[]
这个不是和json定义违背了吗?：

数组（在中括号中）

对象（在大括号中）

难道关联数组在PHP中是对象，而索引数组就不是对象，那它们的区别是什么????

Answer 1

    A string is a sequence of zero or more Unicode characters [UNICODE].
   Note that this citation references the latest version of Unicode
   rather than a specific release.  It is not expected that future
   changes in the UNICODE specification will impact the syntax of JSON.

   An object is an unordered collection of zero or more name/value
   pairs, where a name is a string and a value is a string, number,
   boolean, null, object, or array.

   An array is an ordered sequence of zero or more values.

http://www.faqs.org/rfcs/rfc7...

对象:无序的一系列值
数组：有序的一系列值

这是json的标准说明，所以没毛病

Answer 2

没毛病啊
'{"msg":13,"infor":24,"ra1":[{"msg":13,"infor":24},{"msg":13,"infor":24},{"msg":13,"infor":24},123,3243]}'
ral的值是数组，所以用[]包含。
然后值的前三个又是一个json对象

Answer 3

json_encode()只将索引数组（indexed array）转为数组格式，而将关联数组（associative array）转为对象格式.