2D arrays in JSON getting converted into a 1D array of objects

Question

I've looked around but haven't found an answer so I figured i would give it an ask myself.

I've noticed that a round trip to JSON converts a 2-D array into a 1D array of Objects.

Is there any way around this or should I just try to work with objects from the beginning (e.g. $test->1->4 ? see example below

    $test = array();
    $test[0][0] = "0-0";
    $test[0][2] = "0-2";
    $test[1][1] = "1-1";
    $test[1][2] = "1-2";
    var_dump($test);
    $encoded = json_encode($test);
    var_dump($encoded);
    $recreated = json_decode($encoded);
    var_dump($recreated);

outputs

array(2) {
  [0]=>
  array(2) {
    [0]=>
    string(3) "0-0"
    [2]=>
    string(3) "0-2"
  }
  [1]=>
  array(2) {
    [1]=>
    string(3) "1-1"
    [2]=>
    string(3) "1-2"
  }
}
string(45) "[{"0":"0-0","2":"0-2"},{"1":"1-1","2":"1-2"}]"
array(2) {
  [0]=>
  object(stdClass)#19 (2) {
    ["0"]=>
    string(3) "0-0"
    ["2"]=>
    string(3) "0-2"
  }
  [1]=>
  object(stdClass)#20 (2) {
    ["1"]=>
    string(3) "1-1"
    ["2"]=>
    string(3) "1-2"
  }
}

ckruse · Accepted Answer · 2012-02-22 15:42:44Z

2

This is because you don't have ongoing indexes in your array:

$test = array();
$test[0][0] = "0-0";
$test[0][2] = "0-2";

In this case json_encode() HAS to create an object because there is a numeric key (1) missing.

You can decode it back to an array with json_decode($txt, true), but this is only a work around, not a fix.

answered Feb 22, 2012 at 15:42

ckruse

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2 Comments

paullb Over a year ago

THanks for the answer, that worked. In my particular application, it will be a 256x256 array but chances are every index won't be set. Would it be better to work with objects in the first place? Is there a performance difference?

ckruse Over a year ago

There is no real performance difference on the JS side. On the PHP side there may be a small difference, but I would use arrays with json_decode($txt, true) or set the non-existing indexes to NULL - dunno what fits your needs.

devNoise · Accepted Answer · 2012-02-22 15:36:49Z

0

By default json_decode will convert the json into objects. You code needs to look like:

$recreated = json_decode($encoded, true);

answered Feb 22, 2012 at 15:36

devNoise

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Comments

Louis-Philippe Huberdeau · Accepted Answer · 2012-02-22 15:37:23Z

0

You can decode as arrays:

$recreated = json_decode($encoded, true);

answered Feb 22, 2012 at 15:37

Louis-Philippe Huberdeau

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