php 魔术方法 __clone __toString(五)__clone()- 当对象克隆的时候自动加载此方法
__toString()- 当对象需要echo打印输出的时候自动加载此方法
__clone()
<?phpclass example{ public static $pa; public $pb; public function __construct(){ $this->pb = ++self::$pa; } public function __clone(){ $this->pb = 'no zuo no die'; }}$a = new example;$b = new example;$c = clone $b;$b->pb = 'I Love You So Much!';echo $a->pb;echo '<hr/>';echo $b->pb;echo '<hr/>';echo $c->pb;echo '<hr/>';echo $b->pb;?>
结果如下
1------------------------------------------------------------------------------------I Love You So Much!------------------------------------------------------------------------------------no zuo no die /*要不是有__clone()这个魔术方法，这边的结果应该是2*/------------------------------------------------------------------------------------I Love You So Much!
php手册给了我们一个例子有些难以看懂，如下
<?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();$obj2 = clone $obj;PRint("Original Object:\n");print_r($obj);print("Cloned Object:\n");print_r($obj2);?>
最后的结果
Original Object:MyCloneable Object( [object1] => SubObject Object ( [instance] => 1 ) [object2] => SubObject Object ( [instance] => 2 ))Cloned Object:MyCloneable Object( [object1] => SubObject Object ( [instance] => 3 /*可能这里比较难以理解，其实就是$obj2当克隆的时候将最后的instance为2的结果克隆，并且再执行SubObject::__clone方法*/ ) [object2] => SubObject Object ( [instance] => 2 ))
__toString()
<?php// Declare a simple classclass TestClass{ public $foo; public function __construct($foo) { $this->foo = $foo; } public function __toString() { return $this->foo; }}$class = new TestClass('Hello');echo $class;?>
结果
Hello