From an array, group items based on the key value with PHP

Question

I've this multidimensional array in PHP:

Array
(
    [0] => Array
        (
            [continent] => Europa
            [country] => France
            [capital] => Paris
        )

    [1] => Array
        (
            [continent] => Europa
            [country] => Spain
            [capital] => Madrid
        )
    [2] => Array
        (
            [continent] => Asia
            [country] => Russia
            [capital] => Moscow
        )
)

How can I group countries depending the continent ?

So countries in the same continent should be group together.

The desired output should be:

Array
(
    [Europa] => Array
        (
            [country] => France
            [capital] => Paris
        ),
        (
            [country] => Spain
            [capital] => Madrid
        )
    [Asia] => Array
        (
            [country] => Russia
            [capital] => Moscow
        )
)

How it is possible with PHP please ?

Thanks.

Please show what you have tried already... or do you want somebody to write the code for you? — Honk der Hase, Apr 13 '19 at 13:00
This will help: https://stackoverflow.com/questions/7574857/group-array-by-subarray-values — Nick, Apr 13 '19 at 13:00
This is very easy. Try it and you will see that you did yourself. It's the most basic use of associative arrays. — nice_dev, Apr 13 '19 at 13:15
The specific answer most suitable for this question is https://stackoverflow.com/a/39208133/2943403 — mickmackusa, Feb 23 '23 at 12:42

score 1 · Answer 1 · answered Apr 13 '19 at 13:18

You can create a new array variable, loop through your data array checking to see if the key has already been created and if not, create it and add the related data to that key.

<?php
// $data: the name of your array
$grouped_data = array();

for ($i = 0; $i < count($data); $i++) {
    $key = $data[$i]['continent'];

    if (!isset($grouped_data[$key])) {
        $grouped_data[$key] = array();
    }

    $grouped_data[$key][] = array(
        'country' => $data[$i]['country'],
        'capital' => $data[$i]['capital']
    );
}
?>

`if (!isset($grouped_data[$key])) { $grouped_data[$key] = array(); }` is completely unnecessary in this snippet. — mickmackusa, Feb 23 '23 at 12:35

Jared Farrish · Accepted Answer · 2019-04-13T14:29:05.517

$groupByContinent = function(array $list) {
    return array_reduce($list, function($grouped, $item) {
        $grouped[$item['continent']][] = $item;
        return $grouped;
    }, []);
};

$groupedByContinent = $groupByContinent($data);

https://3v4l.org/s6X1c

Or:

$groupByProperty = function(array $list, string $property) {
    return array_reduce($list, function($grouped, $item) use(&$property) {
        $grouped[$item[$property]][] = $item;
        return $grouped;
    }, []);
};

$groupedByContinent = $groupByProperty($data, 'continent');

https://3v4l.org/Be3HL

Naveed · Answer 3 · 2019-04-13T14:21:29.633

You can also try:

$data = array(
    array(  
        "continent" => "Europa",
        "country" => "France",
        "capital" => "Paris",
        ),
   array(
       "continent" => "Europa",
       "country" => "Spain",
       "capital" => "Madrid",
       ),
   array(
       "continent" => "Asia",
       "country" => "Russia",
       "capital" => "Moscow",
       )
);


$group_by = 'continent';
$attributes = array( 'country', 'capital' );

$output = array();
foreach( $data as $country ) {

    if( isset( $country[$group_by] ) ) {

        $one = array();
        foreach( $attributes as $attribute ) {
            if( isset( $country[$attribute] ) ) {
                $one[$attribute] = $country[$attribute];
            }
        }
        $output[ $country[$group_by] ][] = $one;
     }
}


print_r($output);

Demo

From an array, group items based on the key value with PHP

3 Answers3