developing-with-php

name	developing-with-php
description	Modern PHP 8.x development with type system, attributes, enums, error handling, and Composer. Use when writing PHP code or working with PHP projects. Use when this capability is needed.
metadata	{"author":"fortiumpartners"}

PHP Skill - Quick Reference

Core PHP language patterns for modern development. For Laravel-specific patterns, see the Laravel skill.

Progressive Disclosure: This is the quick reference. See REFERENCE.md for comprehensive patterns, advanced examples, and deep-dives.

Table of Contents

1. PHP 8.x Type System
2. Constructor Property Promotion
3. Enums
4. Match Expression & Named Arguments
5. Attributes
6. Null Safety
7. OOP Essentials
8. Handler/Service Pattern
9. Map/DTO Pattern
10. PDO Database Access
11. Composer & Autoloading
12. Error Handling
13. Testing with PHPUnit
14. Array Operations Quick Reference
15. Security Essentials
16. Quick Reference Tables
17. Related Resources

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PHP 8.x Type System

<?php
// Union types (8.0+)
function process(string|int $value): string|false { }

// Intersection types (8.1+)
function handle(Countable&Iterator $collection): void { }

// Nullable types
function find(int $id): ?User { }

// Never return type (8.1+)
function fail(): never {
    throw new Exception('Fatal error');
}

// True, false, null as standalone types (8.2+)
function isValid(): true { return true; }

Constructor Property Promotion

<?php
// Promoted properties (8.0+) - replaces boilerplate
class User {
    public function __construct(
        private string $name,
        private string $email,
        private bool $active = true,
    ) {}
}

// Readonly class (8.2+) - all properties are readonly
readonly class ValueObject {
    public function __construct(
        public string $value,
        public DateTimeImmutable $createdAt,
    ) {}
}

Enums

<?php
// Backed enum with values (8.1+)
enum Status: string {
    case Draft = 'draft';
    case Published = 'published';
    case Archived = 'archived';

    public function label(): string {
        return match($this) {
            self::Draft => 'Draft',
            self::Published => 'Published',
            self::Archived => 'Archived',
        };
    }
}

// Usage
$status = Status::Published;
$value = $status->value;                 // 'published'
$all = Status::cases();                  // Array of all cases
$fromValue = Status::from('draft');      // Status::Draft
$tryFrom = Status::tryFrom('invalid');   // null (no exception)

See REFERENCE.md for EnumTrait pattern and advanced enum usage.

Match Expression & Named Arguments

<?php
// Match returns value, uses strict comparison
$result = match($status) {
    Status::Draft => 'Not ready',
    Status::Published => 'Live',
    Status::Archived => 'Hidden',
};

// Multiple conditions
$category = match($code) {
    200, 201, 204 => 'success',
    400, 422 => 'client_error',
    500, 502, 503 => 'server_error',
    default => 'unknown',
};

// Named arguments (skip defaults, any order)
$user = createUser(
    email: '[e-mail]',
    name: 'John Doe',
    role: 'admin',
);

Attributes

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

class UserController {
    #[Route('/users', 'GET')]
    public function index(): array { }
}

// Reading attributes via reflection
$reflection = new ReflectionMethod(UserController::class, 'index');
$attributes = $reflection->getAttributes(Route::class);
$route = $attributes[0]->newInstance();
echo $route->path;  // '/users'

Null Safety

<?php
// Null coalescing
$name = $user->name ?? 'Anonymous';

// Null coalescing assignment
$data['count'] ??= 0;

// Nullsafe operator (8.0+)
$country = $user?->address?->country?->name;

// Combined
$timezone = $user?->settings?->timezone ?? 'UTC';

---

OOP Essentials

Interfaces & Abstract Classes

<?php
interface RepositoryInterface {
    public function find(int $id): ?object;
    public function save(object $entity): void;
}

abstract class BaseHandler {
    public function __construct(protected PDO $db) {}
    abstract public function handle(array $data): mixed;
}

Traits

<?php
trait Timestamps {
    protected ?DateTimeImmutable $createdAt = null;

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

class User {
    use Timestamps;
}

See REFERENCE.md for trait conflict resolution, late static binding, and magic methods.

---

Handler/Service Pattern

<?php
class UserHandler {
    public function __construct(
        private readonly PDO $db,
        private readonly CacheInterface $cache,
    ) {}

    public function get(int $id): ?array {
        $cacheKey = "user:{$id}";
        if ($cached = $this->cache->get($cacheKey)) {
            return $cached;
        }

        $stmt = $this->db->prepare('SELECT * FROM users WHERE id = ?');
        $stmt->execute([$id]);
        $user = $stmt->fetch(PDO::FETCH_ASSOC);

        if ($user) {
            $this->cache->set($cacheKey, $user, 3600);
        }
        return $user ?: ;
    }
}

See REFERENCE.md for CRUD handlers, aggregation patterns, and collection mapping.

---

Map/DTO Pattern

<?php
readonly class UserMap {
    public function __construct(
        public int $id,
        public string $name,
        public string $email,
    ) {}

    public static function fromRow(array $row): self {
        return new self(
            id: (int) $row['id'],
            name: trim($row['first_name'] . ' ' . $row['last_name']),
            email: $row['email'],
        );
    }

    public function toArray(): array {
        return ['id' => $this->id, 'name' => $this->name, 'email' => $this->email];
    }
}

See REFERENCE.md for nested mapping and collection patterns.

---

PDO Database Access

Connection

<?php
$dsn = 'mysql:host=localhost;dbname=myapp;charset=utf8mb4';
$options = [
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
    PDO::ATTR_EMULATE_PREPARES => false,
];
$pdo = new PDO($dsn, 'username', 'password', $options);

Prepared Statements

<?php
// Named parameters
$stmt = $pdo->prepare('SELECT * FROM users WHERE email = :email');
$stmt->execute(['email' => $email]);
$user = $stmt->fetch();

// Positional parameters
$stmt = $pdo->prepare('SELECT * FROM users WHERE id = ?');
$stmt->execute([$id]);

Transactions

<?php
try {
    $pdo->beginTransaction();
    // Multiple operations...
    $pdo->commit();
} catch (Exception $e) {
    $pdo->rollBack();
    throw $e;
}

See REFERENCE.md for stored procedures, batch operations, and SQL file execution.

---

Composer & Autoloading

composer.json Essentials

{
    "require": {
        "php": "^8.2"
    },
    "autoload": {
        "psr-4": {
            "App\\": "src/"
        }
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\\": "tests/"
        }
    }
}

Version Constraints

Constraint	Meaning
^1.0	>=1.0.0 <2.0.0
~1.2	>=1.2.0 <1.3.0
1.0.*	>=1.0.0 <1.1.0

---

Error Handling

Exception Pattern

<?php
class AppException extends Exception {
    public function __construct(
        string $message,
        int $code = 0,
        public readonly array $context = [],
    ) {
        parent::__construct($message, $code);
    }
}

class NotFoundException extends AppException {
    public function __construct(string $resource, int|string $id) {
        parent::__construct("{$resource} not found", 404, ['id' => $id]);
    }
}

Exception Handling

<?php
try {
    $user = $handler->findOrFail($id);
} catch (NotFoundException $e) {
    return ['error' => $e->getMessage(), 'code' => 404];
} catch (AppException $e) {
    $this->logger->error($e->getMessage(), $e->context);
    return ['error' => 'An error occurred', 'code' => 500];
}

See REFERENCE.md for global exception handlers and validation exceptions.

---

Testing with PHPUnit

<?php
use PHPUnit\Framework\TestCase;
use PHPUnit\Framework\Attributes\Test;

class UserHandlerTest extends TestCase
{
    private UserHandler $handler;

    protected function setUp(): void
    {
        $pdo = new PDO('sqlite::memory:');
        $this->handler = new UserHandler($pdo);
    }

    #[Test]
    public function it_creates_a_user(): void
    {
        $id = $this->handler->create(['name' => 'John', 'email' => '[e-mail]']);
        $this->assertIsInt($id);
        $this->assertGreaterThan(0, $id);
    }
}

See REFERENCE.md for data providers, mocking, and integration testing.

---

Array Operations Quick Reference

<?php
// Mapping
$names = array_map(fn($u) => $u['name'], $users);

// Filtering
$active = array_filter($users, fn($u) => $u['active']);

// Reducing
$total = array_reduce($items, fn($sum, $i) => $sum + $i['price'], 0);

// Column extraction
$emails = array_column($users, 'email');
$byId = array_column($users, null, 'id');  // Index by 'id'

// Sorting
usort($users, fn($a, $b) => $a['name'] <=> $b['name']);

See REFERENCE.md for generators and advanced collection patterns.

---

Security Essentials

Password Hashing

<?php
$hash = password_hash($password, PASSWORD_DEFAULT);
if (password_verify($password, $hash)) { /* valid */ }

SQL Injection Prevention

<?php
// NEVER: $sql = "SELECT * FROM users WHERE id = {$_GET['id']}";
// ALWAYS: Use prepared statements
$stmt = $pdo->prepare('SELECT * FROM users WHERE id = ?');
$stmt->execute([$_GET['id']]);

Input Validation

<?php
$email = filter_var($_POST['email'], FILTER_VALIDATE_EMAIL);
$cleanHtml = htmlspecialchars($input, ENT_QUOTES | ENT_HTML5, 'UTF-8');

See REFERENCE.md for CSRF protection and comprehensive security patterns.

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Quick Reference Tables

Type Declarations

Type	PHP Version	Example
?Type (nullable)	7.1+	?int
void	7.1+	function f(): void
mixed	8.0+	function f(mixed $x)
Type1|Type2 (union)	8.0+	int|string
never	8.1+	function f(): never
Type1&Type2 (intersection)	8.1+	A&B
true, false, null	8.2+	function f(): true

PDO Fetch Modes

Mode	Returns
PDO::FETCH_ASSOC	Associative array
PDO::FETCH_OBJ	stdClass object
PDO::FETCH_CLASS	Instance of specified class

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Related Resources

• REFERENCE.md - Comprehensive patterns and advanced examples
• examples/ - Real-world code examples
• templates/ - Boilerplate templates
• Laravel Skill - Laravel-specific patterns

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