array_column returning 0 results from an array with data

Question

I have some data coming into a page with multiple rows and columns. I am specifically looking to take 1 entire column and put it into another array.

I am using codeigniter and php. The var dump on my page shows that the data in its raw array is arriving just fine. But once I start to try and create a second array on the page, the array returns 0 results.

Here is the var_dump for the original array. For your sanity, ill only post the first sequence.

array(7) { [0]=> object(stdClass)#19 (7) { ["id"]=> string(1) "1"
["serial_number"]=> string(9) "battery 1" ["battery_type"]=> string(4) "Lipo" ["cell_count"]=> string(1) "4" ["capacity"]=> string(4) "16.8" ["date_submitted"]=> string(19) "0000-00-00 00:00:00" ["user_id_submitted"]=> string(0) "" } [1]=>

Here is the array_column function

<?php 
    $serialnumber = array_column($batteryDb, "serial_number");
    var_dump($serialnumber);
?>

and here is the result:

array(0) { }

Well, seems that $batteryDb has not the right structure. It has to be an array of arrays. Would you be so nice to add the output of var_dump($batteryDb); to your original post - maybe just two items. — Jens A. Koch
– Jens A. Koch, Commented Jul 7, 2016 at 17:34
@JustinSellers Edit your OP to include your sample array data. — topshot
– topshot, Commented Jul 7, 2016 at 17:36

Jens A. Koch · Accepted Answer · 2016-07-07 17:51:36Z

5

Ok, var_dump($batteryDb); shows this:

array(7) { 
 [0] => object(stdClass)#19 (7) {                     <----- object  !!
    ["id"]=> string(1) "1" 
    ["serial_number"]=> string(9) "battery 1" 
    ["battery_type"]=> string(4) "Lipo" 
    ["cell_count"]=> string(1) "4" 
    ["capacity"]=> string(4) "16.8" 
    ["date_submitted"]=> string(19) "0000-00-00 00:00:00" 
    ["user_id_submitted"]=> string(0) "" }
 [1] =>

The problem is that this array structure isn't working with array_column on PHP5.

You have an array of objects, but the function expects an array of arrays.

An array of objects on array_column is only supported by PHP7. Referencing: https://github.com/php/php-src/blob/PHP-7.0.0/UPGRADING#L626

The basic solution would be to turn your objects into arrays:

array(7) { 
     [0] => array (7) {                              <----- array !!
        ["id"]=> string(1) "1"

You can do that using:

$array = (array) $object;
$array = get_object_vars($object);
if multi-dimensional: $array = json_decode(json_encode($object), true);

Give this a try:

$batteryDbArray = json_decode(json_encode($batteryDb), true);

$serial_numbers = array_column($batteryDbArray, 'serial_number');
var_dump($serial_numbers);

edited Jul 7, 2016 at 17:51

answered Jul 7, 2016 at 17:45

Jens A. Koch

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2 Comments

Justin Sellers Over a year ago

ok, so I gave that a try. it rendered this array(7) { [0]=> string(9) "battery 1" [1]=> string(9) "battery 2" [2]=> string(9) "battery 3" [3]=> string(9) "battery 5" [4]=> string(9) "battery 6" [5]=> string(9) "battery 4" [6]=> string(9) "battery 7" }

Justin Sellers Over a year ago

Now to figure out how to put those into a drop down list. haha

Brandon Horsley · Accepted Answer · 2016-07-07 17:53:56Z

1

I think array_column only added support for an array of Objects in 7.0, so you can try upgrading PHP or use a different method.

Try array_map:

$serial_numbers = array_map(function($e) {
  return is_object($e) ? $e->serial_number : $e['serial_number'];
}, $batteryDb);

There are other, worse, solutions, such as using json_encode(json_decode()) or iterating the array converting stdClass to array objects with get_object_vars or casting, but I think these add unnecessary overhead and are less obvious:

$serial_numbers = array_column(json_decode(json_encode($batteryDb), true), 'serial_number'));

answered Jul 7, 2016 at 17:53

Brandon Horsley

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