// Медленный вариант
if (array_key_exists('key', $array)) { }

// Быстрый вариант
if (isset($array['key'])) { }

opcache.enable=1
opcache.memory_consumption=128
opcache.max_accelerated_files=10000
opcache.validate_timestamps=1

$data = ['name' => 'John', 'age' => 25];

// Медленный вариант
$serialized = serialize($data);

// Быстрый вариант
$json = json_encode($data);

$var = null;
var_dump(isset($var)); // false

$var = "0";
var_dump(empty($var)); // true, хотя строка не null

if ($var === null) { /* Переменная null */ }
if ($var === '') { /* Пустая строка */ }
if ($var === 0) { /* Число 0 */ }

if (count($var) === 0) { /* Массив пуст */ }

$stmt = $pdo->prepare("SELECT * FROM users WHERE email = :email");
$stmt->execute(['email' => $email]);
$user = $stmt->fetch();

$stmt = $pdo->query("SELECT id, name FROM users");

CREATE INDEX idx_email ON users(email);

foreach ($users as $user) {
    $stmt = $pdo->prepare("SELECT * FROM orders WHERE user_id = ?");
    $stmt->execute([$user['id']]);
    $orders[$user['id']] = $stmt->fetchAll();
}

$query = "SELECT users.id, users.name, orders.id as order_id
          FROM users 
          LEFT JOIN orders ON users.id = orders.user_id";
$stmt = $pdo->query($query);
$result = $stmt->fetchAll();

$cacheKey = "users_list";
$users = $redis->get($cacheKey);

if (!$users) {
    $users = $pdo->query("SELECT id, name FROM users")->fetchAll();
    $redis->setex($cacheKey, 3600, json_encode($users));
}

function sendSms(string $phoneNumber, string $message): void

final class PhoneNumber
{
    public function __construct(private string $number)
    {
        if (!preg_match('/^\+7\d{10}$/', $number)) {
            throw new InvalidArgumentException('Invalid phone number');
        }
    }

    public function value(): string
    {
        return $this->number;
    }
}

function sendSms(PhoneNumber $phoneNumber, Message $message): void

class UserCollection
{
    /** @var User[] */
    private array $users = [];

    public function __construct(array $users = [])
    {
        foreach ($users as $user) {
            $this->add($user);
        }
    }

    public function add(User $user): void
    {
        $this->users[] = $user;
    }

    public function all(): array
    {
        return $this->users;
    }

    public function filterByActive(): self
    {
        return new self(array_filter($this->users, fn(User $u) => $u->isActive()));
    }

    // и так далее
}

up:
 @cp .env.example .env || true
 @php artisan key:generate
 @composer install
 @npm install
 @php artisan migrate
 @php artisan db:seed
 @npm run dev
 @php artisan serve

use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;

public function boot()
{
    DB::listen(function ($query) {
        if (app()->bound('exception.logged')) {
            Log::channel('sql')->debug($query->sql, $query->bindings);
        }
    });

    app()->singleton('exception.logged', function () {
        return true;
    });

    app()->error(function (\Throwable $e) {
        app()->instance('exception.logged', true);
    });
}

ray($user);
ray($order)->blue();
ray()->showQueries();

composer require spatie/laravel-ray --dev