PHP教程：高效合并与汇总对象数组中重复数据

[
  {
    "user_id": 2,
    "point": 2
  },
  {
    "user_id": 16,
    "point": 3
  },
  {
    "user_id": 2,
    "point": 10
  },
  {
    "user_id": 2,
    "point": 10
  }
]

[
  {
    "user_id": 2,
    "point": 22
  },
  {
    "user_id": 16,
    "point": 3
  }
]

<?php

$jsonData = '[
  {
    "user_id": 2,
    "point": 2
  },
  {
    "user_id": 16,
    "point": 3
  },
  {
    "user_id": 2,
    "point": 10
  },
  {
    "user_id": 2,
    "point": 10
  }
]';

// 将JSON字符串解码为PHP关联数组
$users = json_decode($jsonData, true);

// 此时 $users 的结构为：
/*
Array
(
    [0] => Array ( [user_id] => 2 [point] => 2 )
    [1] => Array ( [user_id] => 16 [point] => 3 )
    [2] => Array ( [user_id] => 2 [point] => 10 )
    [3] => Array ( [user_id] => 2 [point] => 10 )
)
*/
?>

<?php
// ... (接上一步的代码)

$groupedById = array_reduce($users, function ($accumulator, $user) {
  // 以 user_id 作为键，将对应的用户记录添加到累加器中
  $accumulator[$user['user_id']][] = $user;
  return $accumulator;
}, []); // 初始累加器为一个空数组

// 此时 $groupedById 的结构为：
/*
Array
(
    [2] => Array
        (
            [0] => Array ( [user_id] => 2 [point] => 2 )
            [1] => Array ( [user_id] => 2 [point] => 10 )
            [2] => Array ( [user_id] => 2 [point] => 10 )
        )
    [16] => Array
        (
            [0] => Array ( [user_id] => 16 [point] => 3 )
        )
)
*/
?>

<?php
// ... (接上一步的代码)

$result = [];
foreach ($groupedById as $userId => $userRecords) {
    // 使用 array_column 获取当前用户所有记录的 'point' 值，形成一个新数组
    $points = array_column($userRecords, 'point');
    // 使用 array_sum 对 'point' 值数组求和
    $sumPoints = array_sum($points);

    // 将汇总结果添加到最终结果数组中
    $result[] = ['user_id' => $userId, 'point' => $sumPoints];
}

// 此时 $result 的结构为：
/*
Array
(
    [0] => Array ( [user_id] => 2 [point] => 22 )
    [1] => Array ( [user_id] => 16 [point] => 3 )
)
*/
?>

<?php
// ... (接上一步的代码)

echo json_encode($result, JSON_PRETTY_PRINT); // JSON_PRETTY_PRINT 使输出更易读

// 输出结果：
/*
[
    {
        "user_id": 2,
        "point": 22
    },
    {
        "user_id": 16,
        "point": 3
    }
]
*/
?>

<?php

$jsonData = '[
  {
    "user_id": 2,
    "point": 2
  },
  {
    "user_id": 16,
    "point": 3
  },
  {
    "user_id": 2,
    "point": 10
  },
  {
    "user_id": 2,
    "point": 10
  }
]';

// 1. 将JSON字符串解码为PHP关联数组
$users = json_decode($jsonData, true);

// 2. 根据 user_id 进行分组
$groupedById = array_reduce($users, function ($accumulator, $user) {
  $accumulator[$user['user_id']][] = $user;
  return $accumulator;
}, []);

// 3. 计算每个分组的 point 总和并构建最终结果数组
$result = [];
foreach ($groupedById as $userId => $userRecords) {
    $sumPoints = array_sum(array_column($userRecords, 'point'));
    $result[] = ['user_id' => $userId, 'point' => $sumPoints];
}

// 4. 将最终结果编码为JSON字符串并输出
echo json_encode($result, JSON_PRETTY_PRINT);

?>