<?phpclass SubObject{static $instances = 0;public $instance;public function __construct() {$this->instance = ++self::$instances;}public function __clone() {$this->instance = ++self::$instances;}}class MyCloneable{public $object1;public $object2;function __clone(){// 强制复制一份this->object, 否则仍然指向同一个对象$this->object1 = clone $this->object1;}}$obj = new MyCloneable();$obj->object1 = new SubObject();$obj->object2 = new SubObject();