PHP Multidimensional Associative Array to JS Object Using json_encode()

Question

I am perplexed and cannot figure out why this JSON object code is not coming out like I think it should.

For reasons not important to theis example, the PHP array is created from another array. As a PHP array, this works fine.

for($i=0;$i<$FileCount;$i++)
{
    $FileList[$i] = array
    (
        "Category" => $Category, "FileName" => $FileName, "Ext" => $Ext, "Title" => $Title, "ShortName" => $ShortName
    );
}

print_r($FileList);
Array ( [0] => Array ( [Category] => AntiqueGlass [FileName] => AntiqueGlass-BlackGlassBox-B [Ext] => jpg [Title] => BlackGlassBox [ShortName] => AntiqueGlass-BlackGlassBox ) [1] => Array ( [Category] => AntiqueGlass [FileName] => AntiqueGlass-BluePicture-B [Ext] => jpg [Title] => BluePicture [ShortName] => AntiqueGlass-BluePicture ) )

I then do this, with the result of the write shown underneath

$json_array=json_encode($FileList);
echo('
<script type="text/javascript">
    var JSFileList = '.json_encode($json_array, JSON_FORCE_OBJECT).';
    document.write(JSFileList);
</script>'."\n");

[{"Category":"AntiqueGlass","FileName":"AntiqueGlass-BlackGlassBox-B","Ext":"jpg","Title":"BlackGlassBox","ShortName":"AntiqueGlass-BlackGlassBox"},{"Category":"AntiqueGlass","FileName":"AntiqueGlass-BluePicture-B","Ext":"jpg","Title":"BluePicture","ShortName":"AntiqueGlass-BluePicture"}]

I believe the result should come out something like this

{"0":("Category":"AntiqueGlass","FileName":"AntiqueGlass-BlackGlassBox-B","Ext":"jpg","Title":"BlackGlassBox","ShortName":"AntiqueGlass-BlackGlassBox")},{"1":("Category":"AntiqueGlass","FileName":"AntiqueGlass-BluePicture-B","Ext":"jpg","Title":"BluePicture","ShortName":"AntiqueGlass-BluePicture")}

The intent is to access the object like this

JSFileList[i].FileName

All my research says this should work. I am at a loss to know what I am doing wrong.

Why use force object? What you ant in JavaScript is an array of objects. Just plain old json_encode will be fine if you only call it once. — Mike Brant
– Mike Brant, Commented Feb 3, 2014 at 6:49
It's really unnecessary, as json_encode will force it anyway, because it is, at lease partly, an associative array. — RationalRabbit
– RationalRabbit, Commented Feb 3, 2014 at 6:53

Dr.Molle · Accepted Answer · 2014-02-03 06:51:44Z

2

You are calling json_encode twice:

$json_array=json_encode($FileList);
//.....
json_encode($json_array, JSON_FORCE_OBJECT);

you must use the JSON_FORCE_OBJECT-option in the first call, after that $json_array already is a String, JSON_FORCE_OBJECT will have no effect there.

Of course the resulting variable JSFileList with the double-encoding will also be a string, when you need to access the object in JS encode it only 1 time(document.write then would print something like [object Object]).

edited Feb 3, 2014 at 6:51

answered Feb 3, 2014 at 6:37

Dr.Molle

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1 Comment

RationalRabbit Over a year ago

As did I, obviously (grin). Got lost somewhere in my experimenting ... And that was the problem.

deceze · Accepted Answer · 2014-02-03 06:15:05Z

0

[{...},{...},{...}]

This is an array of objects. You can access the individual objects by the numeric array index, like JSFileList[2].FileName. It already works as you need it.

Javascript distinguishes between continuously numerically indexed arrays ([]) and associative objects ({}), PHP does not. json_encode encodes all continuously numerically indexed PHP arrays to Javascript arrays, anything else to objects.

answered Feb 3, 2014 at 6:15

deceze♦

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3 Comments

RationalRabbit Over a year ago

The result of JSFileList[0].FileName is [. The result of JSFileList[1].FileName is (. The result of JSFileList[2].FileName is ".

RationalRabbit Over a year ago

CORRECTION: The result of JSFileList[0].FileName is undefined. The result of JSFileList[0] is [ . The result of JSFileList[1] is (, etc.

deceze Over a year ago

Actually yes, because of stackoverflow.com/a/21521138/476. Combine that and my answer.

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