sum specific values in a multidimensional array (php)

问题

I got a multidimensional array like this:

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

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

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

and I'd like to sum the value [cash] of the sub-arrays who got the same value[city] and obtain an array like this:

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

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

How can I do it?

回答1:

Try below code:

<?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);

Output:

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

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

)

Demo:
http://3v4l.org/D8PME

回答2:

Use function array_reduce() to combine the items having the same city:

$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()
);

回答3:

Using any more than one loop (or looping function) to sum the values is inefficient.

Here is a method that uses temporary keys to build the result array and then reindexes the result array after the loop terminates.

Code: (Demo)

$array=[
    ['city' => 'NewYork', 'cash' => '1000'],
    ['city' => 'Philadelphia', 'cash' => '2300'],
    ['city' => 'NewYork', 'cash' => '2000']
];

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

回答4:

Try this:

 $sumArray = array();

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

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

    }

    var_dump($sumArray);

Output:

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

来源：https://stackoverflow.com/questions/28527413/sum-specific-values-in-a-multidimensional-array-php

标签

php

arrays

multidimensional-array

sum