对多维数组中的特定值求和 (php)

Question

我得到了这样一个多维数组：

Totalarray
(
[0] => Array
    (
        [city] => NewYork
        [cash] => 1000
    )

[1] => Array
    (
        [city] => Philadelphia
        [cash] => 2300
    )

[2] => Array
    (
        [city] => NewYork
        [cash] => 2000
    )
)

我想对获得相同值[city]的子数组的值[cash]求和，得到这样的数组：

Totalarray
(
[0] => Array
    (
        [city] => NewYork
        [cash] => 3000
    )

[1] => Array
    (
        [city] => Philadelphia
        [cash] => 2300
    )
)

我该怎么做？

Answer 1

试试下面的代码：

<?php

$arr = array(
        array('city' => 'NewYork', 'cash' => '1000'),
        array('city' => 'Philadelphia', 'cash' => '2300'),
        array('city' => 'NewYork', 'cash' => '2000'),
    );

$newarray = array();
foreach($arr as $ar)
{
    foreach($ar as $k => $v)
    {
        if(array_key_exists($v, $newarray))
            $newarray[$v]['cash'] = $newarray[$v]['cash'] + $ar['cash'];
        else if($k == 'city')
            $newarray[$v] = $ar;
    }
}

print_r($newarray);

输出：

Array
(
    [NewYork] => Array
        (
            [city] => NewYork
            [cash] => 3000
        )

    [Philadelphia] => Array
        (
            [city] => Philadelphia
            [cash] => 2300
        )

)

演示：
http://3v4l.org/D8PME

Answer 2

试试这个：

 $sumArray = array();

    foreach ($arrTotal as $k=>$subArray) {

        foreach ($subArray as $id=>$value) {
            $sumArray[$subArray['city']]+=$value;
        }

    }

    var_dump($sumArray);

输出：

array(2) {
  ["NewYork"]=>
  int(3000)
  ["Philadelphia"]=>
  int(2300)
}

Answer 3

使用函数array_reduce()合并具有相同city的项目：

$input = array(
    array('city' => 'NewYork',      'cash' => '1000'),
    array('city' => 'Philadelphia', 'cash' => '2300'),
    array('city' => 'NewYork',      'cash' => '2000'),
);

$output = array_reduce(
    // Process the input list
    $input,
    // Add each $item from $input to $carry (partial results)
    function (array $carry, array $item) {
        $city = $item['city'];
        // Check if this city already exists in the partial results list
        if (array_key_exists($city, $carry)) {
            // Update the existing item
            $carry[$city]['cash'] += $item['cash'];
        } else {
            // Create a new item, index by city
            $carry[$city] = $item;
        }
        // Always return the updated partial result
        return $carry;
    },
    // Start with an empty list
    array()
);

Answer 4

使用任何一个以上的循环（或循环函数）对值求和是低效的。

这里有一个方法，它使用临时键构建结果数组，然后在循环终止后重新索引结果数组。

新代码：(Demo) 由于“空合并运算符”

，没有迭代函数调用

foreach ($array as $row) {
    $result[$row['city']] = [
        'city' => $row['city'],
        'cash' => ($result[$row['city']]['cash'] ?? 0) + $row['cash']
    ];
}
var_export(array_values($result));

旧代码：(Demo)

foreach($array as $a){
    if(!isset($result[$a['city']])){
        $result[$a['city']] = $a;  // store temporary city-keyed result array (avoid Notices)
    }else{
        $result[$a['city']]['cash'] += $a['cash'];  // add current value to previous value
    }
}
var_export(array_values($result));  // remove temporary keys

输出：

array (
  0 => 
  array (
    'city' => 'NewYork',
    'cash' => 3000,
  ),
  1 => 
  array (
    'city' => 'Philadelphia',
    'cash' => 2300,
  ),
)

对多维数组中的特定值求和 (php)

sum specific values in a multidimensional array (php)

php

arrays

sum

multidimensional-array