новый массив по ключу из другого многомерного массива

<?php
function filterByKey($array, $keyName) {
    $result = [];
    foreach ($array as $item) {
        if (isset($item[$keyName])) {
            $result[] = $item[$keyName];
        }
    }
    return array_unique($result);
}

$array = [
    ['product_id' => 'xxxx', 'name' => 'iphone'],
    ['product_id' => 'yyyy', 'name' => 'samsung'],
    ['product_id' => 'xxxx', 'name' => 'iphone'],
];

$result = filterByKey($array, 'product_id');

print_r($result);