php

What this skill does

# PHP

## Overview

Modern PHP (7.4+/8.x) patterns including typed properties, attributes, and modern OOP features.

---

## Modern PHP Features

### Type System

```php
<?php

declare(strict_types=1);

// Typed properties (PHP 7.4+)
class User
{
    public string $id;
    public string $email;
    public ?string $name = null;
    public bool $active = true;
    public array $roles = [];
    public DateTimeImmutable $createdAt;

    // Constructor promotion (PHP 8.0+)
    public function __construct(
        public readonly string $email,
        public readonly string $name,
        private string $password
    ) {
        $this->id = uniqid();
        $this->createdAt = new DateTimeImmutable();
    }
}

// Union types (PHP 8.0+)
function process(string|int $value): string|int
{
    return is_string($value) ? strtoupper($value) : $value * 2;
}

// Intersection types (PHP 8.1+)
function processIterable(Countable&Iterator $items): int
{
    return count($items);
}

// Return types
function findUser(string $id): ?User
{
    return $this->repository->find($id);
}

function getUsers(): array
{
    return $this->repository->findAll();
}

// Never return type (PHP 8.1+)
function fail(string $message): never
{
    throw new RuntimeException($message);
}

// Nullable types
function setName(?string $name): void
{
    $this->name = $name;
}
```

### Attributes (PHP 8.0+)

```php
<?php

use Attribute;

// Define attribute
#[Attribute(Attribute::TARGET_PROPERTY)]
class Column
{
    public function __construct(
        public string $name,
        public string $type = 'string',
        public bool $nullable = false
    ) {}
}

#[Attribute(Attribute::TARGET_METHOD)]
class Route
{
    public function __construct(
        public string $path,
        public string $method = 'GET'
    ) {}
}

#[Attribute(Attribute::TARGET_CLASS)]
class Entity
{
    public function __construct(
        public string $table
    ) {}
}

// Using attributes
#[Entity(table: 'users')]
class User
{
    #[Column(name: 'id', type: 'uuid')]
    public string $id;

    #[Column(name: 'email', type: 'string')]
    public string $email;

    #[Column(name: 'name', nullable: true)]
    public ?string $name;
}

class UserController
{
    #[Route(path: '/users', method: 'GET')]
    public function index(): array
    {
        return $this->userService->getAll();
    }

    #[Route(path: '/users/{id}', method: 'GET')]
    public function show(string $id): User
    {
        return $this->userService->find($id);
    }
}

// Reading attributes
$reflection = new ReflectionClass(User::class);
$attributes = $reflection->getAttributes(Entity::class);

foreach ($attributes as $attribute) {
    $instance = $attribute->newInstance();
    echo $instance->table; // 'users'
}
```

### Enums (PHP 8.1+)

```php
<?php

// Basic enum
enum Status
{
    case Pending;
    case Active;
    case Inactive;

    public function label(): string
    {
        return match ($this) {
            self::Pending => 'Pending Review',
            self::Active => 'Active',
            self::Inactive => 'Inactive',
        };
    }
}

// Backed enum (with values)
enum Role: string
{
    case Admin = 'admin';
    case Moderator = 'moderator';
    case User = 'user';

    public function permissions(): array
    {
        return match ($this) {
            self::Admin => ['read', 'write', 'delete', 'admin'],
            self::Moderator => ['read', 'write', 'delete'],
            self::User => ['read', 'write'],
        };
    }

    public static function fromString(string $value): self
    {
        return self::from($value);
    }

    public static function tryFromString(string $value): ?self
    {
        return self::tryFrom($value);
    }
}

// Usage
$status = Status::Active;
echo $status->label(); // "Active"

$role = Role::Admin;
echo $role->value; // "admin"

$userRole = Role::from('user');
$permissions = $userRole->permissions();
```

---

## Object-Oriented Patterns

### Traits

```php
<?php

// Trait definition
trait Timestampable
{
    protected ?DateTimeImmutable $createdAt = null;
    protected ?DateTimeImmutable $updatedAt = null;

    public function getCreatedAt(): ?DateTimeImmutable
    {
        return $this->createdAt;
    }

    public function getUpdatedAt(): ?DateTimeImmutable
    {
        return $this->updatedAt;
    }

    public function touch(): void
    {
        $now = new DateTimeImmutable();
        $this->createdAt ??= $now;
        $this->updatedAt = $now;
    }
}

trait SoftDeletable
{
    protected ?DateTimeImmutable $deletedAt = null;

    public function delete(): void
    {
        $this->deletedAt = new DateTimeImmutable();
    }

    public function restore(): void
    {
        $this->deletedAt = null;
    }

    public function isDeleted(): bool
    {
        return $this->deletedAt !== null;
    }
}

// Using traits
class Document
{
    use Timestampable;
    use SoftDeletable;

    public function __construct(
        public string $title,
        public string $content
    ) {
        $this->touch();
    }
}

// Trait conflict resolution
trait A
{
    public function hello(): string
    {
        return 'Hello from A';
    }
}

trait B
{
    public function hello(): string
    {
        return 'Hello from B';
    }
}

class MyClass
{
    use A, B {
        A::hello insteadof B;
        B::hello as helloFromB;
    }
}
```

### Interfaces and Abstract Classes

```php
<?php

// Interface
interface Repository
{
    public function find(string $id): ?object;
    public function findAll(): array;
    public function save(object $entity): void;
    public function delete(string $id): void;
}

// Generic-style interface
interface Collection
{
    public function add(mixed $item): void;
    public function remove(mixed $item): bool;
    public function contains(mixed $item): bool;
    public function count(): int;
    public function toArray(): array;
}

// Abstract class
abstract class BaseRepository implements Repository
{
    public function __construct(
        protected PDO $pdo,
        protected string $table
    ) {}

    abstract protected function hydrate(array $row): object;

    public function find(string $id): ?object
    {
        $stmt = $this->pdo->prepare(
            "SELECT * FROM {$this->table} WHERE id = :id"
        );
        $stmt->execute(['id' => $id]);
        $row = $stmt->fetch(PDO::FETCH_ASSOC);

        return $row ? $this->hydrate($row) : null;
    }

    public function findAll(): array
    {
        $stmt = $this->pdo->query("SELECT * FROM {$this->table}");
        return array_map(
            fn(array $row) => $this->hydrate($row),
            $stmt->fetchAll(PDO::FETCH_ASSOC)
        );
    }
}

// Concrete implementation
class UserRepository extends BaseRepository
{
    public function __construct(PDO $pdo)
    {
        parent::__construct($pdo, 'users');
    }

    protected function hydrate(array $row): User
    {
        return new User(
            id: $row['id'],
            email: $row['email'],
            name: $row['name']
        );
    }

    public function findByEmail(string $email): ?User
    {
        // Custom method
    }
}
```

---

## Error Handling

```php
<?php

// Custom exceptions
class AppException extends Exception
{
    public function __construct(
        string $message,
        public readonly string $code,
        public readonly array $context = [],
        ?Throwable $previous = null
    ) {
        parent::__construct($message, 0, $previous);
    }
}

class ValidationException extends AppException
{
    public function __construct(
        public readonly array $errors,
        ?Throwable $previous = null
    ) {
        parent::__construct(
            'Validation failed',
            'VALIDATION_ERROR',
            ['errors' => $errors],
            $previous
        );
    }
}

class NotFoundException extends AppException
{
    public function __construct(
        string $resource,
        string $id,
        ?Throwable