How do I get php `json_encode` to return a Javascript array instead of a Javascript object?

Question

I have an array in PHP which contains a list of objects:

// This is a var_dump of $data

array(3911) {
  [0]=>
  object(stdClass)#44 (3) {
    ["ID"]=>
    string(1) "1"
    ["name"]=>
    string(9) "Forest"
  }
  [1]=>
  object(stdClass)#43 (3) {
    ["ID"]=>
    string(1) "2"
    ["Name"]=>
    string(3) "Lt. Dan"
  }

  // etc ...
}

I am converting that array into a flat index based array:

$return = [];
$length = count($data);
$return = array_fill(0, $length, null);

// Convert list into flat array
foreach ( $data as $item ){
  $return[(int)$item->ID] = $item->name;
}

header( 'Content-Type: application/json' );
echo json_encode( $return );

The result I'm getting with json_encode is an object list:

{"0":null,"1":"Forest","2":"Lt. Dan","3":"Bubba","4":"Jenny"}

What I am expecting to get is:

[null,"Forest","Lt. Dan","Bubba","Jenny"]

How do I get `json_encode` to return a Javascript array instead of a Javascript object?

Side note: The Manual says that:

When encoding an array, if the keys are not a continuous numeric sequence starting from 0, all keys are encoded as strings, and specified explicitly for each key-value pair.

But my array is a continous set, that's why I am using array_fill.

Could you add your $data object to this post, or at least the relevant parts of it? — Andy Noelker
– Andy Noelker, Commented Apr 20, 2016 at 13:13
Why array_fill? Why $item->ID when it's just a list? Works here 3v4l.org/SWhE0 — danopz
– danopz, Commented Apr 20, 2016 at 13:14
@copynpaste Read the last line of my question, I'm using array fill because json_encode expects the array to be a sequential list and my ID's aren't always sequential. — hitautodestruct
– hitautodestruct, Commented Apr 20, 2016 at 18:24

Yan Foto · Accepted Answer · 2016-04-21 08:59:06Z

3

UPDATE:

To rephrase the problem:

desired is an array for which indices correspond to IDs of given objects. For every missing ID, the array item at that index must be null.

from the provided example, it can be seen that IDs of objects in $data are zero indexed, so we initialize and array with a length of max(ID) + 1 and fill it as you did previously. However and IMHO, I think this would be a misuse of array data structure. If you have huge gaps in your IDs, your array would contain a big number of nulls. Since JS doesn't have associative arrays, the best option would be to convert your array into an object (as PHP did in your case).

Since $data is not given, this is the best what I came up with:

generally json_encode returns an object if you have an associative array, otherwise, you'll get a normal JSON array. So you might wanna try something like this:

echo json_encode( array_values($return) );

edited Apr 21, 2016 at 8:59

answered Apr 20, 2016 at 13:16

Yan Foto

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5 Comments

hitautodestruct Over a year ago

I added an example of my $data list. array_value won't work because I want to transform the ID into the index of the array.

Yan Foto Over a year ago

This answer was based upon your provided example. You should've mentioned that IDs are not sequential. In that case the answer from @miken32 is the right solution.

hitautodestruct Over a year ago

Thanks for the effort, I did not know my ID's were not sequential and so did not mention it :(

Yan Foto Over a year ago

@hitautodestruct I am updating the answer just for the reference :)

Yan Foto Over a year ago

@hitautodestruct note that you have to have max(ID) + 1 as array length.

miken32 · Accepted Answer · 2016-04-20 18:52:12Z

0

If your IDs aren't sequential, then count($data) is not going to give the results you are looking for. For example, if $data has keys 1, 2, 3, and 5; then array_fill will only give you keys 0-3 on $return, and you'll end up with a non-sequential array.

Try this instead:

$return = [];
$length = max(array_keys($data));
$return = array_fill(0, $length, null);

answered Apr 20, 2016 at 18:52

miken32

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1 Comment

hitautodestruct Over a year ago

This is not 100% a solution to my issue as I had to get the max ID and not the max index in the first array but you pointed me to the right ally! Thanks!

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