Counting Values in Multidimensional Array

Question

I currently have the following array:

Array(
        [0] => Array
            (
                [user] => Name 1
                [group] => 1
            )
        [1] => Array
            (
                [user] => Name 2
                [group] => 1
            )
        [2] => Array
            (
                [user] => Name 3
                [group] => 2
            )
        [3] => Array
            (
                [user] => Name 4
                [group] => 2
            )
        [4] => Array
            (
                [user] => Name 5
                [group] => 3
            )
)

I am attempting to create a new array with the various group values as the key, then count how many are in each group to give the following:

Array
(
    [1] => 2
    [2] => 2
    [3] => 1
)

I have attempted to use the following, however I get undefined index warnings:

$newArr = array();
foreach ($details['user_groups'] as $key => $value) {
        $newArr[$value['user_groups']]++;
}

(I did check SO for other answers, however couldn't find one attempting to do the same)

just to make sure, you are trying to get the `group` from the first array? — , Apr 18 '12 at 18:32
Yeah, so the range of groups from the first array (i.e. 1-3) as the keys of the new array and then count how many are in each group, again from the first array — lethalMango, Apr 18 '12 at 18:34

Michael Berkowski · Accepted Answer · 2014-09-16T12:07:04.070

15

This can be done with a simple iteration:

$counts = array();
foreach ($array as $key=>$subarr) {
  // Add to the current group count if it exists
  if (isset($counts[$subarr['group']]) {
    $counts[$subarr['group']]++;
  }
  // or initialize to 1 if it doesn't exist
  else $counts[$subarr['group']] = 1;

  // Or the ternary one-liner version 
  // instead of the preceding if/else block
  $counts[$subarr['group']] = isset($counts[$subarr['group']]) ? $counts[$subarr['group']]++ : 1;
}

Update for PHP 5.5

In PHP 5.5, which has added the array_column() function to aggregate an inner key from a 2D array, this can be simplified to:

$counts = array_count_values(array_flip(array_column($array, 'group')));

edited Sep 16 '14 at 12:07

answered Apr 18 '12 at 18:34

Michael Berkowski

267,341
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1

`$counts[$subarr['group']++];` – Apr 18 '12 at 18:35
I did try that Michael using the code I included on my question, however I get undefined index warnings. – lethalMango Apr 18 '12 at 18:36
@gerep Not as you have it :) I was missing a bracket, but already fixed it. – Michael Berkowski Apr 18 '12 at 18:36
@lethalMango Did you try the current version I have there? It will not give undefined index warnings. Initially, I hit the save button before completing the if/else – Michael Berkowski Apr 18 '12 at 18:36
Sorry I saw the first version :) Works a charm, I guessed I had missed something obvious! Thanks – lethalMango Apr 18 '12 at 18:39
is there another way without loop the array? – Oki Erie Rinaldi Sep 16 '14 at 04:46
@OkiErieRinaldi If you have PHP 5.5 (which has `array_column()`) you could do `array_count_values(array_flip(array_column($array, 'group')))`. Otherwise, see the array_map() example another user posted. – Michael Berkowski Sep 16 '14 at 11:00

score 5 · Answer 2 · edited Feb 18 '17 at 01:53

5

This can be done with a simple array_map function

$array = array_map(function($element){
    return $element['group'];
}, $array1);

$array2 = (array_count_values($array));

print_r($array2);

edited Feb 18 '17 at 01:53

Barmar

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answered Dec 19 '13 at 06:32

Vijaysinh Parmar

897
1
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19

Dear,@Vijaysinh Parmar where you defined $array1? – Raham Sep 13 '17 at 15:26
you can refer question array as $array1. – Vijaysinh Parmar Sep 13 '17 at 17:44
Dear @Vijaysinh Parmar thank you for such a prompt response.I used my own one but after your reply I prefer yours.Thank you – Raham Sep 13 '17 at 18:22

score 2 · Answer 3 · answered Apr 18 '12 at 19:00

2

Your initial attempt was close. You were simply using the wrong key inside the loop:

$newArr = array();
foreach ($details['user_groups'] as $key => $value) {
        // What you were using:
        // $newArr[$value['user_groups']]++;

        // What you should be using:
        $newArr[$value['group']]++;
}

answered Apr 18 '12 at 19:00

FtDRbwLXw6

27,774
13
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107

So this was a typo question? I do not endorse snippets that generate Warnings/Notices. – mickmackusa Jun 19 '22 at 22:53

score 0 · Answer 4 · edited Mar 12 '15 at 10:53

0

Try this simple but effective way

$count = call_user_func_array('array_merge_recursive', $Array);
echo count($count['user']).'<br>';
echo count($count['group']).'<br>';

edited Mar 12 '15 at 10:53

Alex

11,115
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answered Mar 12 '15 at 10:28

nimtek123

1
2

score 0 · Answer 5 · edited Mar 25 '20 at 08:18

0

$output = array();
  foreach($data as $key => $value){
    $output[$value['group']]['count']++;
}

$final = array();
foreach($output as $key => $value){
    $final[$key] = $value['count'];    
}

print_r($final);

//out put result:=========
Array(
    [1] => 2
    [2] => 2
    [3] => 1
)

edited Mar 25 '20 at 08:18

sanriot

804
4
13

answered Mar 25 '20 at 06:55

tiya Ra

1
1

Is that *out-put result* or *out-put final*? Please describe why this is the way to solve the problem (compared to, e.g. the more functional approach of existing answers), and how yours works. – greybeard Mar 25 '20 at 09:00

score 0 · Answer 6 · answered Dec 09 '20 at 21:09

You only need two native function calls for this task. Isolate the desired column of data with array_column(), then count the occurrences with array_count_values(). This is the only way that I would code this task in one of my projects.

The added benefit of using array_column() is that if some of your subarrays do not contain the targeted column key, then there will be no Notice/Warning generated. If you were to use a common looping technique or array_map/array_walk() instead, you might need to write conditional checks to prevent the Notices/Warnings.

Code: (Demo)

$array = [
    ['user' => 'Name 1', 'group' => 1],
    ['user' => 'Name 2', 'group' => 1],
    ['user' => 'Name 3', 'group' => 2],
    ['user' => 'Name 4', 'group' => 2],
    ['user' => 'Name 5', 'group' => 3],
];

var_export(
    array_count_values(array_column($array, 'group'))
);

Output:

array (
  1 => 2,
  2 => 2,
  3 => 1,
)

Counting Values in Multidimensional Array

6 Answers6

Update for PHP 5.5

Linked

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