PHP array_filter outputs sometimes index number

Question

I encountered some strange error with array_filter.

My json data looks like this:

{
    "data": [
        {
            "item": "book",
            "date": "9.10."
        },
        {
            "item": "apple",
            "date": "10.10."
        },
        {
            "item": "pen",
            "date": "11.10."
        }
    ]
}

I can remove some objects with this code:

$days_arr = array('9.10.','10.10.');
    $result['data'] = array_filter($my_var['data'], function($v) use ($days_arr)
      {
        return in_array($v['date'], $days_arr);
        });
        return json_encode($result);

Which removes the objects containing a date = 9.10. and 10.10. But the problem: as soon as I use $days_arr = array('9.10.','11.10.');

My output is this:

{
    "data": {
        "0": {
            "item": "book",
            "date": "9.10."
        },
        "1": {
            "item": "pen",
            "date": "11.10"
        }
    }
}

So as you can see, some very strange error happens, the json is completely wrong formatted. 9.10. and 10.10. works, 10.10. and 11.10. destroys the output.

Who can help?

I doubt it actually happens with your given example: eval.in/877329 that being said if you do end up with indices 0,2 remaining (notice the gap) then the equivalent JSON structure will be an object and not an array — apokryfos
– apokryfos, Commented Oct 10, 2017 at 15:15

AbraCadaver · Accepted Answer · 2017-10-10 15:18:47Z

3

Coincidentally, your first example results in consecutive indexes starting at 0, 0 and 1 so json_encode() encodes them as dynamically assigned. The second example yields indexes 0 and 2 so it uses the hard coded values. Use array_values() to re-index:

$result['data'] = array_values($result['data']);
return json_encode($result);

edited Oct 10, 2017 at 15:18

answered Oct 10, 2017 at 15:14

AbraCadaver

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Comments

iainn · Accepted Answer · 2017-10-10 15:14:10Z

0

A couple of important things:

array_filter will preserve the keys of the elements that pass the filter
json_encode will preserve array keys in the output "if the keys are not a continuous numeric sequence starting from 0"

So when your $result array contains array keys 0 and 1, they are skipped in the JSON output. When it contains array keys 0 and 2 (as in your second example), they'll be preserved.

You can avoid your problem by removing the keys in the call to json_encode:

return json_encode(array_values($result));

This will keep the output in the same format as the input. See https://eval.in/877330

answered Oct 10, 2017 at 15:14

iainn

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