PHP中的__clone()

php的__clone()方法对一个对象实例进行的浅复制,对象内的基本数值类型进行的是传值复制，而对象内的对象型成员变量,如果不重写__clone方法,显式的clone这个对象成员变量的话,这个成员变量就是传引用复制,而不是生成一个新的对象.如第28行注释所说

 1  <?php 2     class Account { 3         public $balance; 4          5         public function __construct($balance) { 6             $this->balance = $balance; 7         } 8     } 9  10     class Person {11         private $id;12         private $name;13         private $age;14         public $account;15         16         public function __construct($name, $age, Account $account) {17             $this->name = $name;18             $this->age = $age;19             $this->account = $account;20         }21         22         public function setId($id) {23             $this->id = $id;24         }25         26         public function __clone() {    #复制方法,可在里面定义再clone是进行的操作27             $this->id = 0;28             $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29         }30     }31     32     $person = new Person("peter", 15, new Account(1000));33     $person->setId(1);34     $person2 = clone $person;35     36     $person2->account->balance = 250;37     38     var_dump($person, $person2);39     40  ?>

输出:

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) } }