如何使用 PHP json_encode 用 [] 格式化数组数据

Question

Goal: Use json_encode to format array data into a specified format

This is the needed format for the data after running through PHP json_encode:

NEEDED FORMAT

{
    "top_level_data": [
     {
        "extension": {},
        "sub_level_data1": 0
     }
    ]
}

When I use this PHP:

$data = array('top_level_data' => array('extension' => array(),
                                'sub_level_data1' => 0
                                )
            )
$data = json_encode($data);

I get this incorrect Output:

{
    "top_level_data":{
        "extension":[],
        "sub_level_data1": 0
        }
}

Question: How can I modify my php to include the {} and the [] in the correct places as the Needed Format?

Answer 1

It's not clear how you're generating $data ; if it's by the assignment you show then you can just add an extra layer of array at top_level_data , and cast the extension value to an object:

$data = array('top_level_data' => array(
                                    array('extension' => (object)array(),
                                          'sub_level_data1' => 0
                                          )
                                        )
            );

If however you get the $data from another source, you can modify it like this:

$data['top_level_data']['extension'] = (object)$data['top_level_data']['extension'];
$data['top_level_data'] = array($data['top_level_data']);

Both methods yield this JSON:

{
    "top_level_data": [
        {
            "extension": {},
            "sub_level_data1": 0
        }
    ]
}

Demo on 3v4l.org

Answer 2

json_encode will encode sequence array with [] . The sequence array should has index from 0 to n . For other array, associative array and object will encoded with {} . Use the JSON_FORCE_OBJECT parameter of json_encode all the array will be encoded with {} .

Example:

echo json_encode(range(1,3));                     // [1,2,3]
echo json_encode(array(2=>2));                    // {"2":2}
echo json_encode(range(1,3),JSON_FORCE_OBJECT);   // {"0":1,"1":2,"2":3}
echo json_encode((object)range(1,3));             // {"0":1,"1":2,"2":3}