how to get a slice of a multidimensional array using an array with index keys

Question

I have an array

$arr = [
    [
        'id' => 10,
        'name' => 'John',
        'occupation' => 'engineer',
        'points' => 10
    ],
    [
        'id' => 10, 
        'name' => 'John',
        'occupation' => 'librarian',
        'points' => 14
    ],
    [
        'id' => 7,
        'name' => 'Sarah',
        'occupation' => 'artist',
        'points' => 21
    ],
    [
        'id' => 7,
        'name' => 'Sarah',
        'occupation' => 'teacher',
        'points' => 17
    ],  
    [
        'id' => 10,
        'name' => 'John',
        'occupation' => 'butcher',
        'points' => 7
    ],
    [
        'id' => 7,
        'name' => 'Sarah',
        'occupation' => 'engineer',
        'points' => 9
    ],
    [
        'id' => 25,
        'name' => 'Andreea',
        'occupation' => 'judge',
        'points' => 11
    ]
];

And I use this built in functions to get unique ids:

$people = array_column($arr, 'id', 'id');

And then I use a foreach to get every occurrence of each user in the main array $arr:

foreach($people as $id){
    $keys = array_keys(array_column($arr, 'id'), $id);
}

This is the return:

Array
(
    [0] => 0
    [1] => 1
    [2] => 4
)
Array
(
    [0] => 2
    [1] => 3
    [2] => 5
)
Array
(
    [0] => 6
)

Now in order to build a small array for each person I could loop trough this small arrays that contain the keys from the main array and get the values and ending up with small slices.

But, how can I get the actual $arr values for each person instead of getting just the keys? (using as little resources as possible)

I need the result to be like this:

Array
(
    [10] => Array
        (
            [0] => Array
                (
                    [id] => 10
                    [name] => John
                    [occupation] => engineer
                    [points] => 10
                )

            [1] => Array
                (
                    [id] => 10
                    [name] => John
                    [occupation] => librarian
                    [points] => 14
                )

            [2] => Array
                (
                    [id] => 10
                    [name] => John
                    [occupation] => butcher
                    [points] => 7
                )

        )

    [7] => Array
        (
            [0] => Array
                (
                    [id] => 7
                    [name] => Sarah
                    [occupation] => artist
                    [points] => 21
                )

            [1] => Array
                (
                    [id] => 7
                    [name] => Sarah
                    [occupation] => teacher
                    [points] => 17
                )

            [2] => Array
                (
                    [id] => 7
                    [name] => Sarah
                    [occupation] => engineer
                    [points] => 9
                )

        )

    [25] => Array
        (
            [0] => Array
                (
                    [id] => 25
                    [name] => Andreea
                    [occupation] => judge
                    [points] => 11
                )

        )

)

P.S: I don't need to keep the key index the same.

I tried using a second foreach after getting the keys but i think there should be a way to get them all at once when i'm getting the keys. Maybe i shouldn't even get the keys that way? What i'm more interested in is how could i do this with the least amount of resources — Melody
– Melody, Commented Nov 26, 2019 at 10:55

LF-DevJourney · Accepted Answer · 2019-11-26 11:09:05Z

2

You can do it in a more efficient way,Demo

$result = [];
foreach($arr as $v){
    $result[$v["id"]][] = $v;
}
print_r($result);

answered Nov 26, 2019 at 11:09

LF-DevJourney

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1 Comment

lazyCoder Over a year ago

agreed this is the best and efficient way to solve this problem

Haim Evgi · Accepted Answer · 2019-11-26 11:04:02Z

1

use a function of group by like:

$byGroup = group_by("id", $arr);

function group_by($key, $data) {
    $result = array();

    foreach($array as $val) {
        if(array_key_exists($key, $val)){
            $result[$val[$key]][] = $val;
        }else{
            $result[""][] = $val;
        }
    }

    return $result;
}

answered Nov 26, 2019 at 11:04

Haim Evgi

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3 Comments

Nawin Over a year ago

Did you test the function? actually you will get an undefined index $array error.....

Melody Over a year ago

@Nawin he gave an example in that "like" url.

Melody Over a year ago

@HeimEvgi, how efficient is this method?

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