php-检查2个元素相同并找到总和

Question

I have a JSON returned from the backend service.

$a='{
    "post_id": [
        "1",
        "34",
        "29",
        "35",
        "28",
        "37"
    ],
    "posted_by": [
        "1",
        "1",
        "1",
        "1",
        "1",
        "3"
    ],
    "total_likes": [
        4,
        1,
        1,
        1,
        1,
        1
    ]
}';

JSON has post_id, posted_by and how many likes a post received. I convert it into array for processing in php

$data   =   json_decode($a); 

My array looks like this:

stdClass Object
(
    [post_id] => Array
        (
            [0] => 1
            [1] => 34
            [2] => 29
            [3] => 35
            [4] => 28
            [5] => 37
        )

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

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

)

posted_by is user. and what I'm trying to do is to find how many likes a user received and save that value in a new array. SO, in this case, user 1 received 8 likes and user 3 received 1 like. And,I have to save this in an array.

So, for achieving that, I tried something like this but I didn't get any results. Undefined offset error is shown when the loop executes for the nth time.

$total_likes=0;
        $data2=array();

        for($j=0; $j<sizeof($data['posted_by']);$j++)
        {
            if($data['posted_by'][$j] == $data['posted_by'][$j+1])
            {
                $data2[$j]['user']      =   $data['posted_by'][$j];
                $data2[$j]['likes']     =   $total_likes + $data['total_likes'][$j];
            }

        }

Is there any built in function to do such a check?

Answer 1

I would reccomand something like this :

$data = json_decode($a);
// list of all user sid
$users = array_unique($data['posted_by']);
$listUserLike = [];

foreach($users as $user) {
    $indexes = array_keys($data['posted_by'], $user);
    $likes = array_intersect_key($data['total_likes'], array_flip($indexes));
    $listUserLike[] = ['user' => $user, 'nbLike' => array_sum($likes)];
}

then you would have all the results in $listUserLike

listUserLike = [ ['user' => 1, 'nbLike' => 8], ['user' => 3, 'nbLike' => 1], ]