php在添加其他相应值时合并数组的值

Question

I'm generating the following array in json format

[
  {
    "country": "China",
    "amount": "1"
  },
  {
    "country": "India",
    "amount": "5"
  },
  {
    "country": "India",
    "amount": "317"
  },
  {
    "country": "India",
    "amount": "8"
  },
  {
    "country": "India",
    "amount": "2"
  },
  {
    "country": "United States",
    "amount": "213"
  },
  {
    "country": "Iceland",
    "amount": "263"
  }
]

I've tried merging them with the following code

$newData = array();
    $result = array_reduce(
        $data,
        function($newData, $value) {
            $key = $value['country'];
            if (!isset($newData[$key])) {
                $newData[$key] = $value;
            } else {
                $newData[$key]['amount'] += $value['amount'];
            }
            return $newData;
        },
        $newData
    );

my desired output is

[
  {
    "country": "China",
    "amount": "1"
  },
  {
    "country": "India",
    "amount": "332"
  },
  {
    "country": "United States",
    "amount": "213"
  },
  {
    "country": "Iceland",
    "amount": "263"
  }
]

As you can see the array is merged with all the country values grouped and the amount values added accordingly.

Answer 1

Use a simple foreach loop rather than array_reduce.

$newData = array();
foreach ($data as $e) {
    if (isset($newData[$e['country']])) {
        $newData[$e['country']]['amount'] += $e['amount'];
    } else {
        $newData[$e['country']] = $e;
    }
}
$newData = array_values($newData);