How to build a nested array using nested for using PHP

Question

I'm trying to build an array with this structure. I have all the data on one single intermediate table which contains all the keys (if you see the code below it will be better understood). Basically I need to get this structure of array because I want to build a tree view.

        10
        |---14
        |   |---17
        |   |   |---20
        |   |   |   |---11
        |   |   |   |---12
        |   |   |
        |   |   |---21
        |   |       |---11
        |   |       |---13
        |   |---18
        |       |---30
        |       |   |---11
        |       |   |---14
        |       |
        |       |---31
        |           |---15
        |           |---16
        |---15
            |---16
            |   |---40
            |   |   |---11
            |   |   |---12
            |   |
            |   |---41 
            |       |---13
            |       |---14
            |
            |---19
                |---42
                |   |---11
                |   |---12
                |
                |---43
                    |---13
                    |---14

Of which the logic is as follow

$country_id = 10;

$cities = DB::table('table_general')->select('city_id')->where('country_id', $country_id)->distinct()->get();

foreach($cities as $city){
    $departments = DB::table('table_general')->select('depart_id')->where('city_id', $city->id)
                                                                  ->where('country_id', $country_id)->distinct()->get();

    foreach($departments as $departament){
        $provinces = DB::table('table_general')->select('province_id')->where('depart_id', $departament->id)
                                                                      ->where('city_id', $city->id)
                                                                      ->where('country_id', $country_id)->distinct()->get();

        foreach($provinces as $province){
            $districts = DB::table('table_general')->select('district_id')->where('province_id', $province->id)
                                                                         ->where('depart_id', $departament->id)
                                                                         ->where('city_id', $city->id)
                                                                         ->where('country_id', $country_id)
                                                                         ->distinct()->get();
            foreach($districts as $district){
                // I've tried something like this to build the array
                // But isn't the correct way
                $array = array();

                $array["country"] = $country_id;
                $array["country"][]["city"][] = $city->id;
                $array = array("country" => $country_id, array("city" => $city->id));
            }                                                             
        }
    }
}

How should I build with the best way my arrays to build an array like the example above?

Also, can you show your desired result as an array, instead of a graphical tree? It's hard to tell what you're expecting to be keys, and what you're expecting to be values. — Patrick Q
– Patrick Q, Commented Dec 17, 2019 at 15:50
If I were you I would not do database calls in a loop. It's terrible practice and it will realy hurt your performance. Just do it with single query and joint using district as base for row. Then you can just loop results and build your table the way you tried. — Perfect Square
– Perfect Square, Commented Dec 17, 2019 at 15:53

Josh Toth · Accepted Answer · 2019-12-17 15:56:03Z

1

You're resetting the value of $array on each loop. You need to initialize it before anything happens, and then just add to each array as needed.

Also, it looks like you're using Laravel - if you use Eloquent Models, you can simplify the querying and make it way more efficient! The current setup will not scale well.

Try something like this:

$country_id = 10;
$finalArray = [];
$finalArray[$country_id] = [];


$cities = DB::table('table_general')->select('city_id')->where('country_id', $country_id)->distinct()->get();

foreach($cities as $city){
    $finalArray[$country_id][$city->city_id] = [];

    $departments = DB::table('table_general')->select('depart_id')->where('city_id', $city->id)
                                                                  ->where('country_id', $country_id)->distinct()->get();

    foreach($departments as $departament){
        $finalArray[$country_id][$city->city_id][$department->depart_id] = [];

        $provinces = DB::table('table_general')->select('province_id')->where('depart_id', $departament->id)
                                                                      ->where('city_id', $city->id)
                                                                      ->where('country_id', $country_id)->distinct()->get();

        foreach($provinces as $province){
            $finalArray[$country_id][$city->city_id][$department->depart_id][$province->province_id] = [];

            $districts = DB::table('table_general')->select('district_id')->where('province_id', $province->id)
                                                                         ->where('depart_id', $departament->id)
                                                                         ->where('city_id', $city->id)
                                                                         ->where('country_id', $country_id)
                                                                         ->distinct()->get();
            foreach($districts as $district){
                $finalArray[$country_id][$city->city_id][$department->depart_id][$province->province_id][] = $district->district_id;
            }                                                             
        }
    }
}

var_dump($finalArray);

answered Dec 17, 2019 at 15:56

Josh Toth

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5 Comments

Jonatan Lavado Over a year ago

Thank you. It works as I wanted! It's really appreciated. Now I guess I have to improve the performance of my queries

Josh Toth Over a year ago

@L.Flor awesome! I'd recommend reading here: laravel.com/docs/4.2/eloquent If you set it up well, you can just query like

$districts = District:with([ 'province', 'province.department', 'province.department.city' => function ($q) use($country_id) { $q->where('country_id', $country_id); } ])->get();

... or something similar

Jonatan Lavado Over a year ago

The thing is I do not use migrations and I can't use with. But I have a quick question. What would be the equivalent logic on using array_push() so it will let me use whole objects as item

Josh Toth Over a year ago

Eloquent Models are not dependent on migrations. You can't use with because you don't have models and relations defined. I'm not 100% sure what your last question is but I think you're looking for this: array_push($finalArray[$country_id][$city->city_id][$department->depart_id][$province->province_id], $district);

Jonatan Lavado Over a year ago

Yes. Something like that but starting rom country array_push($finalArray[$country][$city][$departament][$province], $district);

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