从php5以后的版本，类就可以使用魔术方法了。php规定以两个下划线（__）开头的方法都保留为魔术方法，所以建议大家函数名最好不用__开 头，除非是为了重载已有的魔术方法。
目前php已有的魔术方法有 __construct，__destruct，__call，__get，__set，__isset，__unset，__sleep，__wakeup，__toString，__set_state 和 __clone。
下面我们来看看两个魔术方法：__clone()和__toString().
__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()
<?php
class 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
<span>1</span> ------------------------------------------------------------------------------------<span> I Love You So Much! </span>------------------------------------------------------------------------------------<span> no zuo no die /*要不是有__clone()这个魔术方法，这边的结果应该是2*/ </span>------------------------------------------------------------------------------------<span> I Love You So Much!</span>
php手册给了我们一个例子有些难以看懂，如下
<?php
class 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($obj2);
?>
最后的结果
Original <span>Object</span><span>:
MyCloneable </span><span>Object</span><span> (
[object1] </span>=> SubObject <span>Object</span><span> (
[instance] </span>=> <span>1</span><span> )
[object2] </span>=> SubObject <span>Object</span><span> (
[instance] </span>=> <span>2</span><span> )
)
Cloned </span><span>Object</span><span>:
MyCloneable </span><span>Object</span><span> (
[object1] </span>=> SubObject <span>Object</span><span> (
[instance] </span>=> <span>3 <span>/*可能这里比较难以理解，其实就是$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*/</span></span><span> )
[object2] </span>=> SubObject <span>Object</span><span> (
[instance] </span>=> <span>2</span><span> )
)</span>
__toString()
<?php
// Declare a simple class
class 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
以上就介绍了PHP 魔术方法: __clone __toString，包括了PHP魔术方法方面的内容，希望对PHP教程有兴趣的朋友有所帮助。
