<?phpclass Account {    public $balance;    public function __construct($balance) {        $this->balance = $balance;    }}class Person {    private $id;    private $name;    private $age;    public $account;    public function __construct($name, $age, Account $account) {        $this->name = $name;        $this->age = $age;        $this->account = $account;    }    public function setId($id) {        $this->id = $id;    }    public function __clone() {    //复制方法,可在里面定义再clone是进行的操作        $this->id = 0;        $this->account = clone $this->account;    //不加这一句,account在clone是会只被复制引用,其中一个account的balance被修改另一个也同样会被修改    }}$person = new Person("peter", 15, new Account(1000));$person->setId(1);$person2 = clone $person;$person2->account->balance = 250;echo ‘<pre>‘;var_dump($person, $person2);?>

结果
object(Person)#1 (4) {  ["id":"Person":private]=>  int(1)  ["name":"Person":private]=>  string(5) "peter"  ["age":"Person":private]=>  int(15)  ["account"]=>  object(Account)#2 (1) {    ["balance"]=>    int(1000)  }}object(Person)#3 (4) {  ["id":"Person":private]=>  int(0)  ["name":"Person":private]=>  string(5) "peter"  ["age":"Person":private]=>  int(15)  ["account"]=>  object(Account)#4 (1) {    ["balance"]=>    int(250)  }}