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1

I am creating an very large multidimensional array using PHP. Each object contains Name, ID, ParentID and Children. Children is an array of more objects in the same format.

It is critical I name the IDs of each object - this helps me put each object under the correct parent. (In the code below, I use 101, 102 etc.)

However, the problem I am having is when I return the array in JSON using json_encode. Each 'Children' array is being printed as an object, not an array - as shown in the JSON code below.

As I read on another SO thread here, they "are made as objects because of the inclusion of string keys" - although they are numbers, they are still strings.

{
"101": {
    "ID": "101",
    "ParentID": "0",
    "Name": "Root One"
    "Children": {
        "102": {
            "ID": "102",
            "ParentID": "101",
            "Name": "Child One"
        },
        "103": {
            "ID": "103",
            "ParentID": "101",
            "Name": "Child Two",
            "Children": {
                "104": {
                    "ID": "104",
                    "ParentID": "103",
                    "Name": "Child Child One"
                }
            }
        },

Does anyone know how to overcome this issue?

Edit: The JSON should look like this (the square brackets are important!):

[
{
    "ID": "101",
    "ParentID": "0",
    "Name": "Root One",
    "Children": [
        {
            "ID": "102",
            "ParentID": "101",
            "Name": "Child One",
            "Children": [
share|improve this question
    
It's actually because the indices are not contiguous, i.e. there are gaps. –  Jack May 7 '13 at 13:04
    
Also, your "children" ARE objects (from my perspective) and not arrays. Be glad, and let OOP flow within you. –  STT LCU May 7 '13 at 13:20

3 Answers 3

up vote 0 down vote accepted

I have now got a working solution which is fast and works well.

  1. Firstly, as written in SO link from the question;

    In JSON, arrays only have numeric keys, whereas objects have string properties. The inclusion of a array key forces the entire outer structure to be an object by necessity.

    In JSON; Curly braces hold objects ({}), Square brackets hold arrays ([]).

  2. So using a string as a key will result in the json_encode function returning objects, whereas reseting the keys will ensure it creates arrays.

  3. Therefore, just before I return my JSON encoded string, I run a function to reset all the array keys. The code I found on this SO thread (Reset array keys in multidimensional array) was particularly useful!

share|improve this answer
up vote 2 down vote

A JSON array has no explicit indexes, it's just an ordered list. The only JSON data structure that has named keys is an object. The literal should make this quite obvious:

["foo", "bar", "baz"]

This array has no named indices and there isn't any provision to add any.

PHP conflates both lists and key-value stores into one array data type. JSON doesn't.

share|improve this answer
    
associative array has named keys –  mohammad mohsenipur May 7 '13 at 13:25
1  
@mohammad PHP has "associative arrays", JSON doesn't! JSON's "associative arrays" are called objects. –  deceze May 7 '13 at 13:26
    
Thanks, the issue I was having was the structure of the JSON (see my last edit). The problem was caused due to the named keys in my PHP associative array. –  Patrick May 7 '13 at 14:23
up vote 0 down vote

http://php.net/manual/en/function.json-decode.php

Set 2nd parameter of json_decode to true to atleast get assoc arrays.

Aside from that: javascript can't handle non-sequential/non-contiguous array indexes, so as soon as the id's are not sequential, json has no other option then to convert it into "string" indexes.

share|improve this answer
    
Thanks for your answer, it will no doubt be of use in the future, but I was using the returned JSON in jQuery! –  Patrick May 7 '13 at 14:24
    
That hardly changes the fact that javascript can't handle non sequential array keys. Hence neither can JSON. And hence neither can jquery. –  Damien Overeem May 7 '13 at 14:51
    
A downvote without comment 1 year after this post.. one wonders why o.O –  Damien Overeem May 20 at 8:25

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