function mergeAndSort ($arr1, $arr2) {
    $arr1 = [1, 6, 2, 9];
    $arr2 = [10, 5, 1, 2];

    $result = array_unique(array_merge($arr1, $arr2));
    sort($result);

    return $result;
}

$arr1 = [1, 6, 2, 9];
$arr2 = [10, 5,1,2];
$result = mergeAndSort($arr1, $arr2);

print_r($result);