php-development

What this skill does

# PHP Development

> Optimized for current PHP 8.x releases, PHPUnit 11+, Composer 2.x, and PDO-backed MySQL or MariaDB apps.

Expert guidance for building high-quality PHP applications with PHP 8.0+, PDO for secure database access, RESTful API design, and XAMPP environment configuration following official PHP documentation at https://php.net.

- Leverage native parallel subagent dispatch and 200k+ context windows where available.


## Anti-Patterns

- Interpolating SQL directly: Prepared statements are the baseline for correctness and security in PHP data access.
- Mixing request parsing, business rules, and rendering: Tightly coupled scripts are harder to test and evolve into APIs.
- Assuming validation alone prevents XSS: Output encoding still matters when user-controlled content is rendered back to HTML.

## Verification Protocol

Before claiming "skill applied successfully":

1. Pass/fail: The PHP Development implementation names the target runtime, framework version, and affected files.
2. Pass/fail: Build, lint, test, or equivalent local validation is run for the changed surface.
3. Pass/fail: Edge cases for errors, dependency drift, and environment differences are addressed or explicitly out of scope.
4. Pressure-test scenario: Apply the workflow to a change that passes happy-path tests but fails one boundary condition.
5. Success metric: Zero untested success claims; every implementation claim maps to a command or artifact.


## Before and After Example

```php
<?php
// Before
$stmt = $pdo->query("SELECT * FROM users WHERE email = '$email'");
$user = $stmt->fetch();

// After
$stmt = $pdo->prepare('SELECT id, email, password_hash FROM users WHERE email = :email LIMIT 1');
$stmt->execute(['email' => $email]);
$user = $stmt->fetch(PDO::FETCH_ASSOC);
```

Replaces string interpolation with a prepared statement and a narrower result shape.

## Activation Conditions

Use symptom -> action triggers: when one matches, apply this skill and verify with the protocol below.

**Core PHP Development:**
- Building PHP RESTful APIs with proper HTTP methods
- Working with XAMPP (Apache + MySQL + PHP) environment
- Implementing secure database operations with PDO
- Creating authentication and session management systems
- Handling file uploads and form submissions

**Database & Data Layer:**
- Connecting PHP to MySQL/MariaDB with PDO
- Writing prepared statements to prevent SQL injection
- Implementing transaction handling for data integrity
- Creating repository patterns for data access
- Working with MySQLi vs PDO comparisons

**Security & Best Practices:**
- Implementing password hashing (password_hash, password_verify)
- Securing against XSS, CSRF, and SQL injection
- Validating and sanitizing user input
- Managing sessions and authentication tokens
- Configuring CORS headers for API access

**API Development:**
- Designing RESTful endpoints with proper HTTP status codes
- Handling JSON requests and responses
- Implementing middleware for authentication and authorization
- Error handling and logging
- Rate limiting and API versioning

---

## Part 1: PHP 8.0+ Fundamentals

### Modern PHP Features

```php
<?php
// Named arguments (PHP 8.0+)
function createUser(string $name, string $email, bool $isAdmin = false): User {
    return new User($name, $email, $isAdmin);
}

// Call with named arguments
$user = createUser(email: '[email protected]', name: 'John Doe');

// Union types (PHP 8.0+)
function processValue(string|int|float $value): string {
    return (string)$value;
}

// Nullsafe operator (PHP 8.0+)
$country = $session?->user?->address?->country ?? 'Unknown';

// Constructor property promotion (PHP 8.0+)
class User {
    public function __construct(
        public string $name,
        public string $email,
        private string $passwordHash
    ) {}
}
```

### Type Declarations & Strict Types

```php
<?php
declare(strict_types=1); // Enforce type safety

// Typed properties and return types
class Recipe {
    private int $id;
    private string $title;
    private ?DateTime $createdAt;

    public function __construct(int $id, string $title) {
        $this->id = $id;
        $this->title = $title;
    }

    public function getTitle(): string {
        return $this->title;
    }

    public function setCreatedAt(?DateTime $date): void {
        $this->createdAt = $date;
    }
}

// Union and intersection types
function processData(string|array $data): string|int {
    return is_array($data) ? count($data) : strlen($data);
}
```

---

## Part 2: PDO Database Integration

### Database Connection Class

```php
<?php
class Database {
    private static ?PDO $instance = null;

    public static function getInstance(): PDO {
        if (self::$instance === null) {
            $host = $_ENV['DB_HOST'] ?? 'localhost';
            $dbname = $_ENV['DB_NAME'] ?? 'recipe_sharing_system';
            $username = $_ENV['DB_USER'] ?? 'root';
            $password = $_ENV['DB_PASSWORD'] ?? '';
            $charset = 'utf8mb4';

            $dsn = "mysql:host=$host;dbname=$dbname;charset=$charset";

            try {
                self::$instance = new PDO($dsn, $username, $password, [
                    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                    PDO::ATTR_EMULATE_PREPARES => false,
                ]);
            } catch (PDOException $e) {
                error_log("Database connection failed: " . $e->getMessage());
                throw new RuntimeException("Database connection error");
            }
        }

        return self::$instance;
    }
}
```

### Prepared Statements for Security

```php
<?php
class UserRepository {
    private PDO $db;

    public function __construct(PDO $db) {
        $this->db = $db;
    }

    // Find user by email with prepared statement
    public function findByEmail(string $email): ?array {
        $stmt = $this->db->prepare(
            "SELECT id, email, password_hash, role, status
             FROM user
             WHERE email = :email LIMIT 1"
        );

        $stmt->bindParam(':email', $email, PDO::PARAM_STR);
        $stmt->execute();

        $user = $stmt->fetch();
        return $user ?: null;
    }

    // Create new user with password hashing
    public function create(string $name, string $email, string $password): int {
        $passwordHash = password_hash($password, PASSWORD_DEFAULT);

        $stmt = $this->db->prepare(
            "INSERT INTO user (name, email, password_hash, role, status, created_at, updated_at)
             VALUES (:name, :email, :password_hash, 'user', 'active', NOW(), NOW())"
        );

        $stmt->bindParam(':name', $name, PDO::PARAM_STR);
        $stmt->bindParam(':email', $email, PDO::PARAM_STR);
        $stmt->bindParam(':password_hash', $passwordHash, PDO::PARAM_STR);

        $stmt->execute();

        return (int) $this->db->lastInsertId();
    }

    // Authentication with password verification
    public function authenticate(string $email, string $password): ?array {
        $user = $this->findByEmail($email);

        if ($user === null) {
            return null;
        }

        if (!password_verify($password, $user['password_hash'])) {
            return null;
        }

        // Check if password needs rehash
        if (password_needs_rehash($user['password_hash'], PASSWORD_DEFAULT)) {
            $newHash = password_hash($password, PASSWORD_DEFAULT);
            $this->updatePasswordHash($user['id'], $newHash);
        }

        unset($user['password_hash']); // Remove sensitive data
        return $user;
    }

    private function updatePasswordHash(int $userId, string $hash): void {
        $stmt = $this->db->prepare(
            "UPDATE user SET password_hash = :hash WHERE id = :id"
        );
        $stmt->execute([':hash' => $hash, ':id' => $userId]);
    }
}
```

### Transaction Management

```php
<?php
class RecipeService {
    private PDO $db;

    pub