PHP - sum values with the same key - php

Question

What is the best way to sum the 'val' field with the same 'color' for each different color:
Array
(
[0] => Array
(
[color]=> "red"
[val]=> 4
)
[1] => Array
(
[color]=> "green"
[val]=> 3
)
[2] => Array
(
[color]=> "blue"
[val]=> 1
)
[3] => Array
(
[color]=> "green"
[val]=> 6
)
[4] => Array
(
[color]=> "blue"
[val]=> 2
)
)
Desired result : red: 4; green: 9; blue: 3.
Regards,
Elio Fernandes

Answer 1

I would do it this way, with a foreach loop:
$temp = [];
foreach($arr as $value) {
//check if color exists in the temp array
if(!array_key_exists($value['color'], $temp)) {
//if it does not exist, create it with a value of 0
$temp[$value['color']] = 0;
}
//Add up the values from each color
$temp[$value['color']] += $value['val'];
}

Answer 2

You can use array_reduce to have less and more readable code:
$array = array
(
0 => array("color"=> "red","val"=> 4),
1 => array("color"=> "blue","val"=> 3),
2 => array("color"=> "blue","val"=> 1)
);
function sum($accumulator, $item){
$accumulator[$item['color']] = $accumulator[$item['color']] ?? 0;
$accumulator[$item['color']] += $item['val'];
return $accumulator;
}
$sum = array_reduce($array, "sum");
var_dump($sum); // return here array(2) { ["red"]=> int(4) ["blue"]=> int(4) }
And the documentation: http://php.net/manual/en/function.array-reduce.php

Answer 3

I would loop it for readability's sake.
$output = array();
foreach($array as $value){
if(!isset($output[$value['color']])) $output[$value['color']] = 0; //Ensure the value is 0 if it doesn't exist
$output[$value['color']] += $value['val']; //Add the total for that color
}
This will return an array of colors to total counts.

Answer 4

Personally I'd do something like this with array_reduce, but as mentioned above it might not be the most readable option. Definitely a matter of opinion though.
$result = array_reduce($array, function ($carry, $item) {
$carry[$item['color']] = $carry[$item['color']] ?? 0;
$carry[$item['color']] += $item['val'];
return $carry;
}, []);
See https://eval.in/894644
Edit: Fix notices

Answer 5

To keep up the speed, without the foreach loop, I would say to do it like this:
$array = [
[
"color" => "red",
"val" => "4"
],
[
"color" => "green",
"val" => "3"
],
[
"color" => "blue",
"val" => "1"
],
[
"color" => "green",
"val" => "6"
],
[
"color" => "blue",
"val" => "2"
]
];
$array = array_values(array_reduce(
$array,
function (array $a, array $v) {
$k = "".$v['color']."";
if (!array_key_exists($k, $a)) {
$a[$k] = $v;
} else {
$a[$k]['val'] += $v['val'];
}
return $a;
},
array()
));
var_dump($array);

Answer 6

$arrays = array(
array(
"color"=>"red",
"val"=>4
),
array(
"color"=>"green",
"val"=>3
)
);
foreach ($color as $array) {
echo $array["color"].": ".$array["val"].";";
}