sum of unique values in array - php

Question

I have below array $billitems_taxes
[0] => Array
(
[id] => 1
[tax_name] => A
[tax_value] => 12
)
[1] => Array
(
[id] => 2
[tax_name] => A
[tax_value] => 8
)
[2] => Array
(
[id] => 3
[tax_name] => B
[tax_value] => 12
)
and I want output as below, find two common tax_name and do some of same and then create a new array.
[0] => Array
(
[id] => 1
[tax_name] => A
[tax_value] => 20
)
[1] => Array
(
[id] => 3
[tax_name] => B
[tax_value] => 12
)
I tried with below code, but it did not return a correct array.
$return_array = [];
foreach($billitems_taxes as $b)
{
$return_array['tax_name'] = $b->tax_name;
$return_array['tax_value'] += $b->tax_value;
}

Answer 1

First off, you have an array of arrays, not objects.
Then your loop needs to know if it has already seen a this tax name which will already be in the new array to check that I used array_key_exists()
$return_array = [];
foreach($billitems_taxes as $b)
{
if ( array_key_exists($b['tax_name'], $return_array) ) {
$return_array[$b['tax_name']]['tax_value'] += $b['tax_value'];
} else {
$return_array[$b['tax_name']] = $b;
}
}
RESULT
Array(
[A] => Array
([id] => 1
[tax_name] => A
[tax_value] => 20
)
[B] => Array
([id] => 3
[tax_name] => B
[tax_value] => 12
)
)
And if its important for the array to be numerically indexed just add
$return_array = array_values($return_array);
after the end of the loop

Answer 2

You must group by 'tax_name' and must sum 'tax_value'.
$billitems_taxes = [
['id' => 1, 'tax_name' => 'A', 'tax_value' => 12],
['id' => 2, 'tax_name' => 'A', 'tax_value' => 8],
['id' => 3, 'tax_name' => 'B', 'tax_value' => 12]
];
$result = [];
foreach($billitems_taxes as $row){
$groupKey = $row['tax_name'];
if(array_key_exists($groupKey,$result)){
$result[$groupKey]['tax_value'] += $row['tax_value'];
} else {
$result[$groupKey] = $row;
}
}
$result = array_values($result);
echo '<pre>';
var_export($result);
/*
array (
0 =>
array (
'id' => 1,
'tax_name' => 'A',
'tax_value' => 20,
),
1 =>
array (
'id' => 3,
'tax_name' => 'B',
'tax_value' => 12,
),
)
*/
The solution with the external class tableArray is very simple. The result is the same.
$result = tableArray::create($billitems_taxes)
->filterGroupAggregate(['tax_value' => 'SUM'],['tax_name'])
->fetchAll()
;