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

 <?php
    class 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;
    
    var_dump($person, $person2);
    
 ?>

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) } }