单例池（PHP 示例）

Multiton 可以用作单例的容器。这是 Multiton 实现是 Singleton 和 Pool 模式的组合。

这是一个如何创建常见的 Multiton 抽象 Pool 类的示例：

abstract class MultitonPoolAbstract
{
    /**
     * @var array
     */
    protected static $instances = [];

    final protected function __construct() {}

    /**
     * Get class name of lately binded class
     *
     * @return string
     */
    final protected static function getClassName()
    {
        return get_called_class();
    }

    /**
     * Instantiates a calling class object
     *
     * @return static
     */
    public static function getInstance()
    {
        $className = static::getClassName();

        if( !isset(self::$instances[$className]) ) {
            self::$instances[$className] = new $className;
        }

        return self::$instances[$className];
    }

    /**
     * Deletes a calling class object
     *
     * @return void
     */
    public static function deleteInstance()
    {
        $className = static::getClassName();

        if( isset(self::$instances[$className]) )
            unset(self::$instances[$className]);
    }

    /*-------------------------------------------------------------------------
    | Seal methods that can instantiate the class
    |------------------------------------------------------------------------*/

    final protected function __clone() {}

    final protected function __sleep() {}

    final protected function __wakeup() {}
}

这样我们就可以实例化各种 Singleton 池。