PHP 2d数组总和在相同的索引值

Question

So I have 2d array, with some arrays inside. indexes are all same in arrays: "id" and "cost". On same "id" values I want to sum "number" values. Here's my 2d array:

$array = array (
            array ('id' => 2, 'cost' => 300),
            array ('id' => 1, 'cost' => 200),
            array ('id' => 2, 'cost' => 100),
);

I've made some code, but it get's not exactly what i want.

$result = array ();
foreach($array as $item){
  if (isset($result[$item['id']])){
      $result[$item['id']] += $item['cost'];
  }else{
      $result[$item['id']] = $item['cost'];
  }
}
var_dump($result);

Will show me this:

array (size=2)
2 => int 400
1 => int 200

I want it to show me like this:

array (size=2)
 0 => 
  array (size=2)
  'id' => int 2
  'cost' => int 400
 1 => 
  array (size=2)
  'id' => int 1
  'cost' => int 200

Any help would be perfect :)

Answer 1

You can initiate it as an array if the key does not exist. Add the cost if it already exist.

$array = array (
    array ('id' => 2, 'cost' => 300),
    array ('id' => 1, 'cost' => 200),
    array ('id' => 2, 'cost' => 100),
);

$result = array ();
foreach($array as $item){
    if (isset($result[$item['id']])){
            //Add the cost
            $result[$item['id']]["cost"] += $item['cost'];
    } else {
            //Init as array
            $result[$item['id']] = array( "id" => $item['id'], "cost" => $item['cost'] );
    }
}

This will result to:

Array
(
    [2] => Array
        (
            [id] => 2
            [cost] => 400
        )

    [1] => Array
        (
            [id] => 1
            [cost] => 200
        )

)

Answer 2

You can use foreach and array_values for the desired result

$array = array (
        array ('id' => 2, 'cost' => 300),
        array ('id' => 1, 'cost' => 200),
        array ('id' => 2, 'cost' => 100),
);
$res = [];
foreach($array as $key => $value){

  array_key_exists($value['id'], $res) ? (
    $res[$value['id']]['cost'] += $value['cost']
  )
  :
  (
    $res[$value['id']] = [
        'id' => $value['id'],
        'cost' => $value['cost']
    ]
  );

}
echo '<pre>';
print_r(array_values($res));

Result

Array
(
[0] => Array
    (
        [id] => 2
        [cost] => 400
    )

[1] => Array
    (
        [id] => 1
        [cost] => 200
    )

)

Live Demo