merge_array returns null if one or more of arrays is empty?

Question

I will give you quick run down of what I am doing.

I am using wordpress with the advanced custom fields plugin. This is a php based question because these get_field() fields contain object arrays.

$gallery_location   = get_field('gallery_location');
$gallery_studio = get_field('gallery_studio');

For example $gallery_location when dumped will return this...

array(18) {
  [0]=>
  array(10) {
    ["id"]=>
    int(126)
    ["alt"]=>
    string(0) ""
    ["title"]=>
    string(33) "CBR1000RR STD Supersport 2014 001"
    ["caption"]=>
    string(0) ""
    ["description"]=>
    string(0) ""
    ["mime_type"]=>
    string(10) "image/jpeg"
    ["url"]=>
    string(94) "http://www.example.com/wp/wp-content/uploads/2013/10/CBR1000RR-STD-Supersport-2014-001.jpg"
    ["width"]=>
    int(7360)
    ["height"]=>
    int(4912)
  }
... on so fourth
}

I am then using merge_array to merge both objects...

$gallery_location = get_field('gallery_location');
$gallery_studio = get_field('gallery_studio');

$downloads = array_merge( $gallery_location, $gallery_studio );

I am merging multiple arrays but if one of the arrays is empty then this is causing the merge array to return null entirely!

My question is how can I stop merge_array returning null is some of the arrays are empty?

Thanks in advance for any ideas.

@zessx

This is what I am returning...

$gallery_location   = get_field( 'gallery_location' );
$gallery_studio     = get_field( 'gallery_studio' );

$downloads = array_merge( $gallery_location, $gallery_studio );

var_dump($gallery_location);

var_dump($gallery_studio);

var_dump($downloads);

and these are the results of dumps above in same order...

string(0) ""

array(18) {
  [0]=>
  array(10) {
    ["id"]=>
    int(126)
    ["alt"]=>
    string(0) ""
    ["title"]=>
    string(33) "CBR1000RR STD Supersport 2014 001"
    ["caption"]=>
    string(0) ""
    ["description"]=>
    string(0) ""
    ["mime_type"]=>
    string(10) "image/jpeg"
    ["url"]=>
    string(94) "http://www.example.com/wp/wp-content/uploads/2013/10/CBR1000RR-STD-Supersport-2014-001.jpg"
    ["width"]=>
    int(7360)
    ["height"]=>
    int(4912)
  }
... on so fourth
}

NULL

As you can see $downloads is still returning null, if I try and use both your solution below it does not work?

Seems good. Have you tried your `var_dump($gallery_location); var_dump($gallery_studio);` just before your `array_merge` ? — zessx, Oct 31 '13 at 16:47
@zessx - I've just updated my question, it's becuase one of the arrays are empty which cause merge to return null overall :/ — Joshc, Oct 31 '13 at 16:48

score 78 · Accepted Answer · edited Nov 24 '15 at 00:21

78

array_merge only accepts arrays as parameters. If one of your parameters is null, it will raise an error :

Warning: array_merge(): Argument #x is not an array...

This error won't be raised if one of the arrays is empty. An empty array is still an array.

Two options :

1/ Force the type to be array

$downloads = array_merge( (array)$gallery_location, (array)$gallery_studio );

2/ Check if variables are arrays

$downloads = array();
if(is_array($gallery_location))
    $downloads = array_merge($downloads, $gallery_location);
if(is_array($gallery_studio ))
    $downloads = array_merge($downloads, $gallery_studio);

PHP Sandbox

edited Nov 24 '15 at 00:21

Geoffrey Hale

10,597
5
44
45

answered Oct 31 '13 at 16:53

zessx

68,042
28
135
158

This does not seem to result the null issue, please see my question above at the bottom, I have dumped everything so you can see what empty arrays are returning. Thanks for your help so far. – Joshc Oct 31 '13 at 17:14
There was a typo (`downlads` instead of `downloads`), but it should work, [see this PHP sandbox](http://sandbox.onlinephpfunctions.com/code/7512b59a0e08de604fcb1a87e8ba68d2fb1e57f3) – zessx Oct 31 '13 at 17:43
I love you so much dude this now works - sorry I was concentration, it was a cheap copy and paste on my behalf. Thanks for you help man. +1 – Joshc Oct 31 '13 at 18:03
Adding `(array)` is definitely the nicer way to handle this +1 – AO_ Feb 09 '16 at 10:49
2

Just a note, since the `?:` operator is available now, one can also do `array_merge($a1 ?: [], $a2 ?: [], $a3 ?: [], $a4 ?: []);` which is essentially the same as casting to `(array)` but a bit less typing – billrichards May 17 '21 at 15:40

score 4 · Answer 2 · edited Jun 11 '16 at 05:58

4

You can use the following way for merger your arrays:

$c = (array)$a + (array)$b

edited Jun 11 '16 at 05:58

slfan

8,950
115
65
78

answered Jun 11 '16 at 05:38

Константин Дмитриенко

41
3

merge_array returns null if one or more of arrays is empty?

2 Answers2

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