Advent of code 2016/4

Ajax Direct

$real_rooms = $input->lines->map(function ($room) {
    preg_match("/([a-z\-]+)\-([0-9]+)\[([a-z]+)\]/", $room, $matches);
    [$_, $letters, $sector, $checksum] = $matches;

    $value = set(str_split($letters))->remove("-")
        ->occurrences()
        ->sortKeys()->sort(fn ($a, $b) => $b <=> $a)
        ->keys()->slice(0, 5)->join("");

    if ($value == $checksum) return compact("letters", "sector", "checksum");
    return false;

})->filter();

// ==================================================
// > PART 1
// ==================================================
$solution_1 = $real_rooms->column("sector")->sum();

// ==================================================
// > PART 2
// ==================================================
foreach ($real_rooms as $room) {
    $decode = "";
    foreach (str_split($room["letters"]) as $i=>$letter) {
        if ($letter != "-") $decode[$i] = chr(((ord($letter) - 96) + $room["sector"]) % 26 + 96);
    }

    if (strpos($decode , "northpole") !== false) break;
}

$solution_2 = $room["sector"];