Key ordering when json_encode php variable (array) into javascript variable

Question

When try to json_encode a php array variable into javascript variable have an issue:

var duration_options = <?=json_encode($duration_options)?>;
        var duration_options_items = '';
        $.each(duration_options,function(index, value) {
            if(init_act_duration == value){
                var selected_option = 'selected=selected';
                }else{
                var selected_option = '';
            }
            duration_options_items = duration_options_items + '<option value="'+index+'" '+selected_option+'>'+value+'</option>';
        });

        duration_options_items = '<select class="form-control select2 select_ajax select_ajax_duration" name="edit_activity_duration" style="width:100%">'+duration_options_items+'</select>';

The PHP array is

    Array
(
    [0.5] => 0.5
    [1] => 1
    [1.5] => 1.5
    [2] => 2
    [2.5] => 2.5
    [3] => 3
    [3.5] => 3.5
    [4] => 4
)

After json_encode when I use that json in my javascript the array is like:

  Array
    (

        [1] => 1
        [2] => 2
        [3] => 3
        [4] => 4
        [0.5] => 0.5
        [1.5] => 1.5
        [2.5] => 2.5
        [3.5] => 3.5
    )

Just can't understand it why and have no idea how to ordering them properly

After json_encode becomes: ... Is that really a Javascript array? — hindmost
– hindmost, Commented Apr 21, 2016 at 10:17
check this:- eval.in/557376 . It clearly states that you are doing something with your array before json_encode — Death-is-the-real-truth
– Death-is-the-real-truth, Commented Apr 21, 2016 at 10:24
Please edit the question and post your code. Don't just assume PHP is broken ;-) — Álvaro González
– Álvaro González, Commented Apr 21, 2016 at 10:26
@Anant Not necessarily, just paste the encoded json in your browser console (chrome in my case), and you'll see the reordered version. Problem is, the question is probably missing the "when I use that json in my javascript..." portion. — Yoshi
– Yoshi, Commented Apr 21, 2016 at 10:26
Just use json_encode(array_values($duration_options));, the decimal keys don't make much sense anyway (keys are equal to values). — Yoshi
– Yoshi, Commented Apr 21, 2016 at 10:32

MarcoS · Accepted Answer · 2016-04-21 10:25:26Z

2

You are observing this behaviour because your array does not contain integer and sequential keys. So, json_encode maps it to a JSON object.

answered Apr 21, 2016 at 10:25

MarcoS

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Comments

Álvaro González · Accepted Answer · 2016-04-21 10:50:23Z

2

I presume you assume the JSON is wrong but you haven't really inspected it (there're several ways to do so, such as the Net pane in your browser's developer tools).

As soon as you parse it from JavaScript it becomes a JavaScript object. As such, the order of keys is not guaranteed because that's how the ECMAScript spec defines objects.

If you need bullet-proof order, you need to switch to regular arrays, i.e., with consecutive zero-based integer keys.

answered Apr 21, 2016 at 10:50

Álvaro González

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Comments

user3745228 · Accepted Answer · 2016-04-21 10:22:10Z

-1

And what is the problem with this, you have same keys so you can use them the same? It seems it sort by length key and then natural.

When you loop use keys.

answered Apr 21, 2016 at 10:22

user3745228

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1 Comment

Анжел Миленов Over a year ago

I edited my question to see that I use the json_encode php variable to make select / option dropdown with loop

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