单例模式在PHP框架中的使用与扩展

class Singleton
{
    private static $instance;

    private function __construct()
    {
        // 防止通过 new 关键字创建实例
    }

    public static function getInstance()
    {
        if (!self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }
}

// 使用单例模式
$singleton = Singleton::getInstance();

class Database
{
    private static $instance;
    private $connection;

    private function __construct()
    {
        // 初始化数据库连接
        $this->connection = new PDO('Mysql:host=localhost;dbname=mydb', 'username', 'passWord');
    }

    public static function getInstance()
    {
        if (!self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    public function getConnection()
    {
        return $this->connection;
    }
}

// 使用单例模式获取数据库连接
$db = Database::getInstance()->getConnection();

class Config
{
    private static $instance;
    private $config;

    private function __construct()
    {
        // 初始化配置信息
        $this->config = [
            'db_host' => 'localhost',
            'db_name' => 'mydb',
            'db_user' => 'username',
            'db_password' => 'password',
        ];
    }

    public static function getInstance()
    {
        if (!self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    public function getConfig($key)
    {
        return $this->config[$key] ?? null;
    }
}

// 使用单例模式获取配置信息
$dbHost = Config::getInstance()->getConfig('db_host');

class Singleton
{
    private static $instance = null;

    private function __construct()
    {
        // 在构造函数中进行实例化
    }

    public static function getInstance()
    {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }
}

class Singleton
{
    private static $instance = null;
    private static $lock = null;

    private function __construct()
    {
        // 构造函数内容
    }

    public static function getInstance()
    {
        if (self::$instance === null) {
            self::$lock = new Mutex();
            self::$lock->lock();
            if (self::$instance === null) {
                self::$instance = new self();
            }
            self::$lock->unlock();
        }
        return self::$instance;
    }
}