json_encode() on a multidimensional array - with string keys - php

Question

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": [

Answer 1

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.

Answer 2

This is your object:
$parent=new StdClass();
$parent->ID=101;
$parent->ParentID=0;
$parent->Name='Root One';
$child1=new StdClass();
$child1->ID=1011;
$child1->ParentID=$parent->ID;
$child1->Name='Child One';
$parent->Children[]=$child1;
$child1_1=new StdClass();
$child1_1->ID=10111;
$child1_1->ParentID=$child1->ID;
$child1_1->Name='Child One One';
$child1->Children[]=$child1_1;
This is your JSON convert function:
echo json_encode($parent,JSON_PRETTY_PRINT);
and this is your object coded into JSON format:
{
"ID": 101,
"ParentID": 0,
"Name": "Root One",
"Children": [
{
"ID": 1011,
"ParentID": 101,
"Name": "Child One",
"Children": [
{
"ID": 10111,
"ParentID": 1011,
"Name": "Child One One"
}
]
}
]
}
The answer came later because I started learning PHP later. Anyway, some day, someone might find it useful.

Answer 3

I have now got a working solution which is fast and works well.
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 ([]).
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.
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!

Answer 4

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.