json_encode不保留顺序 [英] json_encode not preserving order

问题描述

我在PHP中有一个多维数组：

I have a multi dimensional array, in PHP:

Array
(
[1] => Array
    (
        [19] => Array
            (                    
                [type] => 2
            )            
        [6] => Array
            (                    
                [type] => 4
            )
        [12] => Array
            (                    
                [type] => 3
            )
    )

)

当我json_encode这个数组在javascript中通过：

When i json_encode this array in javascript via:

 var jsonArray = <?php echo json_encode($above_array); ?>;

我得到：

 Object
 (
 [1] => Object
 (
    [6] => Object
        (                    
            [type] => 2
        )
    [12] => Object
        (                    
            [type] => 4
        )
    [19] => Object
        (                    
            [type] => 3
        )
)

)

我想保留第一个订单而不是第二个订单。

I want to preserve the first order and not the second one by id.

推荐答案

StackOverflow上有一个问题
JavaScript保证对象物业订单？
简而言之，答案是否定的，但事实并非如此。因此，当将PHP数组转换为Javascript对象时，不会保留键顺序。

There's a question on StackOverflow Does JavaScript Guarantee Object Property Order? In short, the answer is no, it doesn't. So when converting a PHP array to a Javascript object, the key order will not be preserved.

PHP和Javascript中的数组之间的主要区别在于后者只能保存从零开始的顺序整数键。因此，并不总是可以将PHP数组转换为Javascript数组。
让我们看几个例子：

The major difference between arrays in PHP and Javascript is that the latter can hold only sequential integer keys starting from zero. So it's not always possible to convert a PHP array to a Javascript array. Let's look at a few examples:

// example 1
echo json_encode(array(0 => 'a', 1 => 'b')) // outputs ["a","b"]

// example 2
echo json_encode(array(0 => 'a', 3 => 'b')) // outputs {"0":"a","3":"b"}

// example 3
echo json_encode(array(3 => 'b', 0 => 'a')) // outputs {"3":"b","0":"a"}, but in Javascript the key order will be the same as in example 2

1. 在第一个示例中， json_encode 将PHP数组转换为相同的Javascript数组。


2. 在第二个例子中，它转换为一个对象，因为键顺序不是顺序的。


3. 在第三个例子中，它也转换为一个东西。但是在Javascript中，对象2和3将是相同的，具有相同的键顺序，即使键以不同的顺序列出。所以它不是 json_encode 不保留键顺序的函数，而是Javascript本身。

1. In the first example, json_encode converts a PHP array into an identical Javascript array.
2. In the second example, it converts to an object, because the keys order is not sequential.
3. In the third example, it also converts to an object. But in Javascript, the objects 2 and 3 will be the same, with the same key order, even though the keys are listed in a different order. So it's not json_encode function that is not preserving the key order, but Javascript itself.

回到我们的问题：如何将PHP数组传递给Javascript，保留关键顺序？
一种方法是将PHP键值对包装到数组中：

Returning to our question: how to pass a PHP array to Javascript preserving the key order? One approach is to wrap PHP key-value pairs into arrays:

// original array:
array(
    3 => 'b', 
    0 => 'a'
)

// must be converted to:
array(
    array(3, 'b'),
    array(0, 'a')
)

然后 json_encode 将导致以下Javascript数组：

Then json_encode will result in the following Javascript array:

[
  [3,"b"],
  [0,"a"]
]

最后一部分是在Javascript中迭代这样一个数组：

And the last part is iterating through such an array in Javascript:

var php_encoded_array = [
  [3,"b"],
  [0,"a"]
];

for (var i=0; i < php_encoded_array.length; i++) {
  var rec = php_encoded_array[i],
      key = rec[0],
      value = rec[1];

  console.log(key + ': ' + value);
}
// It will output:
// 3: b
// 0: a
// Which is the exact same order as in the PHP array

此方法也与非整数键兼容。

This approach is also compatible with non-integer keys.

以下是在PHP端转换数组的代码（在类似问题中由 pr1001 建议）。它适用于一维数组。

Here's the code (suggested by pr1001 in a similar question) for converting an array on the PHP side. It will work for one-dimensional arrays.

array_map(
    function($key, $value) { return array($key, $value); },
    array_keys($data),
    array_values($data)
)

这里是多维数组的递归函数实现：

And here's a recursive function implementation for multi-dimensional arrays:

function array_preserve_js_order(array $data) {
    return array_map(
        function($key, $value) {
            if (is_array($value)) {
                $value = array_preserve_js_order($value);
            }
            return array($key, $value);
        },
        array_keys($data),
        array_values($data)
    );
}

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