<?php
class UserDataProcessor {
    private $pdo;

    public function __construct(PDO $pdo) {
        $this->pdo = $pdo;
        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }

    public function getUserById(int $userId): ?array {
        // Prepared statement to prevent SQL Injection
        $stmt = $this->pdo->prepare("SELECT id, username, email FROM users WHERE id = :id");
        $stmt->bindParam(':id', $userId, PDO::PARAM_INT);
        $stmt->execute();
        return $stmt->fetch(PDO::FETCH_ASSOC);
    }

    public function createUser(string $username, string $email, string $passwordHash): bool {
        $stmt = $this->pdo->prepare("INSERT INTO users (username, email, password_hash) VALUES (:username, :email, :password_hash)");
        $stmt->bindParam(':username', $username, PDO::PARAM_STR);
        $stmt->bindParam(':email', $email, PDO::PARAM_STR);
        $stmt->bindParam(':password_hash', $passwordHash, PDO::PARAM_STR);
        return $stmt->execute();
    }
}

// Example Usage:
// try {
//     $dsn = 'mysql:host=localhost;dbname=mydb;charset=utf8mb4';
//     $pdo = new PDO($dsn, 'user', 'password');
//     $processor = new UserDataProcessor($pdo);

//     $user = $processor->getUserById(123);
//     if ($user) {
//         echo "User found: " . htmlspecialchars($user['username']) . "
";
//     } else {
//         echo "User not found.
";
//     }

//     // Assuming password_hash is already generated securely (e.g., using password_hash() function)
//     // $processor->createUser('newuser', 'new@example.com', 'secure_hash_here');

// } catch (PDOException $e) {
//     error_log("Database Error: " . $e->getMessage());
//     echo "A database error occurred.";
// }