PHP Sum multidimensional array values where certain index is the same

You need to iterate over your results, adding a new entry to the output when you encounter a new team, or updating the points value when you find the same team again. This is most easily done by initially indexing the output by the team name, and then using array_values to re-index the array numerically:

$teams = array();
foreach ($results as $result) {
    $team = $result['team'];
    if (!isset($teams[$team])) {
        $teams[$team] = array('team' => $team, 'points' => $result['punti']);
    }
    else {
        $teams[$team]['points'] += $result['punti'];
    }
}
$teams = array_values($teams);
print_r($teams);

Output (for your sample data):

Array
(
    [0] => Array
        (
            [team] => Red Bull Racing
            [points] => 418
        )
    [1] => Array
        (
            [team] => Scuderia Ferrari
            [points] => 353
        )
    [2] => Array
        (
            [team] => Mercedes-AMG
            [points] => 516
        )
    [3] => Array
        (
            [team] => Racing Point F1
            [points] => 147
        )
    [4] => Array
        (
            [team] => Haas F1
            [points] => 127
        )
)

Demo on 3v4l.org

This should work for arrays like the one of your example ($arr is an array like the one in your example, I haven't defined it here for simplicity's sake):

$res = array();
foreach($arr as $value) {
    foreach($value as $key => $number) {
        (!isset($res[$key])) ?
            $res[$key] = $number :
            $res[$key] += $number;
    }
}

print_r($res);

I need compare values of the products by each key. To highlight rows in the compare table where price, quantity, availability, or manufacturer is different.

If you want to highlight all products unless all of them have exactly the same price, quantity, availability, or manufacturer.

function:

function productsIdentical(array &$products) : bool
{
    if (count($products) < 2) {
        throw new InvalidArgumentException("You should pass at least 2 products to compare");
    }

    $compare = '';
    foreach ($products as $product) {
        ksort($product); //to make comparison of key order insensitive
        $sha = sha1(json_encode($product));
        if (empty($compare)) {
            $compare = $sha;
        } elseif ($sha !== $compare) {
            return false;
        }
    }
    return true;
}

returns true only if all products' fields have exactly the same keys and value, otherwise it returns false

so you use it this way:

$identicalFlag = productsIdentical($all_products);
if ($identicalFlag === false) {
    echo "Products are not identical:" . PHP_EOL;

    $nonIdenticalProductsArr = array_keys($all_products);
    echo "Non identical products are:" . PHP_EOL;
    print_r($nonIdenticalProductsArr);

    //do your styling  on $nonIdenticalProducts

} else {
    echo "Products are identical" . PHP_EOL;
}

Output:

for identical products:

Products are identical

for non identical:

Products are not identical:
Non identical products are:
Array
(
    [0] => product_1
    [1] => product_2
    [2] => product_3
)

Or if you want to detect every product field that is not the same across all products in the array use this function:

function getFieldsNonIdentical(array &$products) : array
{
    if (count($products) < 2) {
        throw new InvalidArgumentException("You should pass at least 2 products to compare");
    }

    $compareArr = [];
    $keyDifferentArr = [];
    foreach ($products as $product) {
        foreach($product as $key => $val) {
            if (!key_exists($key, $compareArr)) {
                $compareArr[$key] = $val;
            } elseif ($compareArr[$key] !== $val) {
                $keyDifferentArr[$key] = true;
            }
        }
    }
    return array_keys($keyDifferentArr);
}

this way:

$fieldsNonIdentical = getFieldsNonIdentical($all_products);

if (!empty($fieldsNonIdentical)) {
    echo "Fields that are non identical:" . PHP_EOL;

    print_r($fieldsNonIdentical);

    //do your styling

    $nonIdenticalStyle = 'style="background-color: lightblue;"';
    $styleArr = [];
    foreach ($fieldsNonIdentical as $key => $value) {
        $styleArr[$value] = $nonIdenticalStyle;
    }

    echo "Non Identical fields styling is:" . PHP_EOL;
    print_r($styleArr);
} else {
    echo "All fields in all products are the same." . PHP_EOL;
}

Output

for identical:

All fields in all products are the same.

for non identical:

Fields that are non identical:
Array
(
    [0] => price
    [1] => manufacturer
)
Non Identical fields styling is:
Array
(
    [price] => style="background-color: lightblue;"
    [manufacturer] => style="background-color: lightblue;"
)