Remove duplicates array from a multidimensional array in PHP

Question

How, from this array, I can filter the duplicate values?

Actually, for the same country and city, the data are the same - Except the population changed.

How can I remove the array that contains the higher population?

$arr = array
(
    "100" => array(
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '1800000',
        ),
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '2000000',
        ),
        array(
            "country" => 'France',
            "city" => 'Toulouse',
            "population" => '500000',
        ),
    )
    "101" => array(
        array(
            "country" => 'Russia',
            "city" => 'Moscow',
            "population" => '144000000',
        )
    )
);

So the desired output should be:

$arr = array
(
    "100" => array(
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '1800000'
        ),
        array(
            "country" => 'France',
            "city" => 'Toulouse',
            "population" => '500000'
        ),
    )
    "101" => array(
        array(
            "country" => 'Russia',
            "city" => 'Moscow',
            "population" => '144000000',
        )
    )
);

This is what I tried:

$temp_array = [];
foreach ($array as &$v) {
    if (!isset($temp_array[$v['country']] && $temp_array[$v['city']]))
        $temp_array[$v[$key]] =& $v;
    }
$array = array_values($temp_array);
return $array;

dWinder · Accepted Answer · 2019-04-14 19:58:11Z

3

You can first use array_reduce for filtering the lower population (use the combination of country and city as key). Then explode them and reset the array with that min value:

foreach($arr as $k => &$ar) {
    $temp = array_reduce($ar, function ($carry, $item) {
        $key = $item["country"] . "###" . $item["city"];
        $carry[$key] = (isset($carry[$key]) && $item["population"] > $carry[$key]) ?  $carry[$key] : $item["population"];
        return $carry;
    }, []);
    $ar = [];
    foreach($temp as $k => $val) {
        list($country, $city) = explode("###", $k);
        $ar[] = array("country" => $country, "city" => $city, "population" => $val);
    }
}

Live example: 3lv4

Edit:

You can use array_filter instead the foreach loop to avoid coping:

$ar = array_filter($ar, function ($item) use ($mins) {
    $key = $item["country"] . "###" . $item["city"];
    return $mins[$key] == $item["population"];
 });

edited Apr 14, 2019 at 19:58

answered Apr 14, 2019 at 19:14

dWinder

11.7k3 gold badges27 silver badges40 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Andreas Over a year ago

"city" = "Moscow" is not part of the question

dWinder Over a year ago

@Andreas it is part of the desire output so assuming OP has typo

Testy Over a year ago

Actually, the problem with your solution is the need to copy/paste the value to pass to the new array $ar[] = array("country" => $country, "city" => $city, "population" => $val);. Thanks.

dWinder Over a year ago

@Testy if the copy bother you use array_filter - edit my post

Testy Over a year ago

Hum. Very good. Could you please update the link? Also could you remove the part with the city ?

|

imposterSyndrome · Accepted Answer · 2019-04-14 19:15:14Z

from the looks of it the array is already grouped by country, i'm assuming that each array element only has child arrays from the same country. I'd also say it's more sensible to have an array with keys for each country anyway for easier access and filtering down the line so I would say

$populations = [];

foreach($array as $arr) {
if(!isset($populations[$arr['country']])) $populations[$arr['country']] = [];//create an array entry for the country
     $cities = [];
     foreach($arr as $city) {
       if(!isset($cities[$city]) || $cities[$city]['population'] > $city['population']) $cities[$city] = ['population' => $city['population']];//you could put the value straight in, but this means if you expand later you could add extra fields to each cities info such as district, number of unemployed or whatever you're using this for

     }
$populations[$arr['country']] = $cities;
}

this is a slightly different output to that which you have outlined, but i think it will make it simpler to use further on as you can access all data for specific countries, and then for cities therein rather than having to continually loop through and check if the child contains a country you are after.

I hope this makes sense, my fiancee is trying to talk to me about ikea at the same time as I'm answering, so it may not be 100% perfect but will point you in a good direction at least

pauldrodriguez · Accepted Answer · 2019-04-14 19:24:27Z

what I did two nested loops, the first gets the subarray that contains all the content for a specific key (e.g. 100 and 101).

next I iterate through the data, and keep a temporary array with two levels, the first will be the country as key, and the second will be the city as key that tracks the lowest population.

once the above is done, I iterate through the temporary array to get the country, city and population in the correct format and append it to a new array. I then substitute the previous array for this newly acquired result.

<?php

$arr = array
(
    "100" => array(
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '1800000',
        ),
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '2000000',
        ),
        array(
            "country" => 'France',
            "city" => 'Toulouse',
            "population" => '500000',
        ),
    ),
    "101" => array(
        array(
            "country" => 'Russia',
            "city" => 'Moscow',
            "population" => '144000000',
        )
    )
);

foreach($arr as $key=>$subarr) {
    $tmp = array();
    foreach($subarr as $v) {
        $country = $v['country'];
        $city = $v['city'];
        $population = $v['population'];

        if(isset($tmp[$country])) {
            if(isset($tmp[$country][$city])) {
                if($tmp[$country][$city] > $population) {
                    $tmp[$country][$city] = $population;
                }
            } else {
                $tmp[$country][$city] = $population;
            }
        } else {
            $tmp[$country] = array();
            $tmp[$country][$city] = $population;
        }
    }

    $res = array();
        foreach($tmp as $country=>$cities) {
            foreach($cities as $city=>$population) {
                $res[] = array('country'=>$country,'city'=>$city,'population'=>$population);
            }
        }
    $arr[$key] = $res;

}
print_r($arr);

Andreas · Accepted Answer · 2019-04-14 20:44:39Z

0

You can make a compound array key with the country and city that way it's easy to keep track of what you have looped.
Since city may not be in the arrays then a if it needed to not get a notice.

foreach($arr as $key => $sub){
    foreach($sub as $item){
        if(isset($item['city'])){
            if(!isset($res[$key][$item['country'] . $item['city']])) $res[$key][$item['country'] . $item['city']] = $item;
            if($res[$key][$item['country'] . $item['city']] < $item['population']) $res[$key][$item['country'] . $item['city']] = $item;
        }else{
            if(!isset($res[$key][$item['country']])) $res[$key][$item['country']] = $item;
            if($res[$key][$item['country']] < $item['population']) $res[$key][$item['country']] = $item;
        }
    }
}
var_dump($res);

Output:

array(2) {
  [100]=>
  array(2) {
    ["FranceParis"]=>
    array(3) {
      ["country"]=>
      string(6) "France"
      ["city"]=>
      string(5) "Paris"
      ["population"]=>
      string(7) "1800000"
    }
    ["FranceToulouse"]=>
    array(3) {
      ["country"]=>
      string(6) "France"
      ["city"]=>
      string(8) "Toulouse"
      ["population"]=>
      string(6) "500000"
    }
  }
  [101]=>
  array(1) {
    ["Russia"]=>
    array(2) {
      ["country"]=>
      string(6) "Russia"
      ["population"]=>
      string(9) "144000000"
    }
  }
}

https://3v4l.org/KNuId

If you need to remove the keys such as "FranceToulouse" then just loop the array again and use array_values

edited Apr 14, 2019 at 20:44

answered Apr 14, 2019 at 19:19

Andreas

24k7 gold badges34 silver badges75 bronze badges

4 Comments

Testy Over a year ago

Hello. Thanks for your time. How can I remove after the key like "FranceParis"? Thanks.

Andreas Over a year ago

I added that to my answer just a few seconds ago. Update the page and it ahould be there

Testy Over a year ago

I can't see it sorry. It keeps echoing the "FranceParis".

Andreas Over a year ago

@Testy I'm flattered that you accepted my answer but I believe dWinders answer is a better answer. It's your decision and you should accept the answer you find best, but I actually think you have not given his answer enough chance.

Collectives™ on Stack Overflow

Remove duplicates array from a multidimensional array in PHP

4 Answers 4

6 Comments

Comments

Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

6 Comments

Comments

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related