PHP中魔术方法的用法

PHP中魔术方法的用法

PHP把所有以__(两个下划线)开头的类方法当成魔术方法。所以你定义自己的类方法时,不要以 __为前缀。

<?php

//1.__toString、__set、__get__isset()、__unset()

/*

The __toString method allows a class to decide how it will react when it is converted to a string.

__set() is run when writing data to inaccessible members.

__get() is utilized for reading data from inaccessible members.

__isset() is triggered by calling isset() or empty() on inaccessible members.

__unset() is invoked when unset() is used on inaccessible members.

*/

class TestClass

{

private $data = array();

public $foo;

public function __construct($foo) {

$this->foo = $foo;

}

public function __toString() {

return $this->foo;

}

public function __set($name, $value) {

echo "__set, Setting '$name' to '$value'\n";

$this->data[$name] = $value;

}

public function __get($name) {

echo "__get, Getting '$name'\n";

if (array_key_exists($name, $this->data)) {

return $this->data[$name];

}

}

/** As of PHP 5.1.0 */

public function __isset($name) {

echo "__isset, Is '$name' set?\n";

return isset($this->data[$name]);

}

/** As of PHP 5.1.0 */

public function __unset($name) {

echo "__unset, Unsetting '$name'\n";

unset($this->data[$name]);

}

}

$obj = new TestClass('Hello');

echo "__toString, $obj\n";

$obj->a = 1;

echo $obj->a . "\n\n";

var_dump(isset($obj->a));

unset($obj->a);

var_dump(isset($obj->a));

echo "\n\n";

//2.__call、__callStatic

/*

mixed __call ( string $name , array $arguments )

mixed __callStatic ( string $name , array $arguments )

__call() is triggered when invoking inaccessible methods in an object context.

__callStatic() is triggered when invoking inaccessible methods in a static context.

The $name argument is the name of the method being called. The $arguments argument is an enumerated array containing the parameters passed to the $name'ed method.

*/

class MethodTest {

public function __call($name, $arguments) {

// Note: value of $name is case sensitive.

echo "__call, Calling object method '$name' "

. implode(', ', $arguments). "\n";

}

/** As of PHP 5.3.0 */

public static function __callStatic($name, $arguments) {

// Note: value of $name is case sensitive.

echo "__callStatic, Calling static method '$name' "

. implode(', ', $arguments). "\n";

}

}

$obj = new MethodTest;

$obj->runTest('in object context', 'param2', 'param3');

//MethodTest::runTest('in static context'); // As of PHP 5.3.0

echo "\n\n";

//3.__invoke

/*

The __invoke method is called when a script tries to call an object as a function.

Note: This feature is available since PHP 5.3.0.

*/

class CallableClass {

function __invoke($x) {

var_dump($x);

}

}

$obj = new CallableClass;

//$obj(5);

var_dump('__invoke: ' . is_callable($obj));

echo "\n\n";

//4.__sleep、__wakeup

/*

串行化serialize可以把变量包括对象,转化成连续bytes数据. 你可以将串行化后的变量存在一个文件里或在网络上传输. 然后再反串行化还原为原来的数据. 你在反串行化类的对象之前定义的类,PHP可以成功地存储其对象的属性和方法. 有时你可能需要一个对象在反串行化后立即执行. 为了这样的目的,PHP会自动寻找__sleep和__wakeup方法.

当一个对象被串行化,PHP会调用__sleep方法(如果存在的话). 在反串行化一个对象后,PHP 会调用__wakeup方法. 这两个方法都不接受参数. __sleep方法必须返回一个数组,包含需要串行化的属性. PHP会抛弃其它属性的值. 如果没有__sleep方法,PHP将保存所有属性.

下面的例子显示了如何用__sleep和__wakeup方法来串行化一个对象. Id属性是一个不打算保留在对象中的临时属性. __sleep方法保证在串行化的对象中不包含id属性. 当反串行化一个User对象,__wakeup方法建立id属性的新值. 这个例子被设计成自我保持. 在实际开发中,你可能发现包含资源(如图像或数据流)的对象需要这些方法

*/

class User

{

public $name;

public $id;

function __construct()

{

//give user a unique ID 赋予一个差别 的ID

$this->id = uniqid();

}

//__sleep返回值的类型是数组,数组中的值是不需要串型化的字段id

function __sleep()

{

//do not serialize this->id 不串行化id

return(array("name"));

}

function __wakeup()

{

//give user a unique ID

$this->id = uniqid();

}

}

//create object 成立一个器材

$u = new User;

$u->name = "Leon";

//serialize it 串行化 留意不串行化id属性,id的值被遗弃

$s = serialize($u);

echo "__sleep, __wakeup, s: $s";

//unserialize it 反串行化 id被重新赋值

$u2 = unserialize($s);

//$u and $u2 have different IDs $u和$u2有差别 的ID

print_r($u);

print_r($u2);

echo "\n\n";

//5、__set_state

/*

This static method is called for classes exported by var_export() since PHP 5.1.0.

The only parameter of this method is an array containing exported properties in the form array('property' => value, ...).

*/

class A

{

public $var1;

public $var2;

public static function __set_state($an_array) // As of PHP 5.1.0

{

//$an_array打印出来是数组,而不是调用时传递的对象

print_r($an_array);

$obj = new A;

$obj->var1 = $an_array['var1'];

$obj->var2 = $an_array['var2'];

return $obj;

}

}

$a = new A;

$a->var1 = 5;

$a->var2 = 'foo';

echo "__set_state:\n";

eval('$b = ' . var_export($a, true) . ';'); // $b = A::__set_state(array(

// 'var1' => 5,

// 'var2' => 'foo',

// ));

var_dump($b);

echo "\n\n";

//6、__clone

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()

{

// Force a copy of this->object, otherwise

// it will point to same object.

$this->object1 = clone $this->object1;

}

}

$obj = new MyCloneable();

$obj->object1 = new SubObject();

$obj->object2 = new SubObject();

$obj2 = clone $obj;

print("__clone, Original Object:\n");

print_r($obj);

print("__clone, Cloned Object:\n");

print_r($obj2);

echo "\n\n";

?>

输出结果如下:

__toString, Hello

__set, Setting 'a' to '1'

__get, Getting 'a'

1

__isset, Is 'a' set?

bool(true)

__unset, Unsetting 'a'

__isset, Is 'a' set?

bool(false)

__call, Calling object method 'runTest' in object context, param2, param3

string(10) "__invoke: "

__sleep, __wakeup, s: O:4:"User":1:{s:4:"name";s:4:"Leon";}User Object

(

[name] => Leon

[id] => 4db1b17640da1

)

User Object

(

[name] => Leon

[id] => 4db1b17640dbc

)

__set_state:

Array

(

[var1] => 5

[var2] => foo

)

object(A)#5 (2) {

["var1"]=>

int(5)

["var2"]=>

string(3) "foo"

}

__clone, Original Object:

MyCloneable Object

(

[object1] => SubObject Object

(

[instance] => 1

)

[object2] => SubObject Object

(

[instance] => 2

)

)

__clone, Cloned Object:

MyCloneable Object

(

[object1] => SubObject Object

(

[instance] => 3

)

[object2] => SubObject Object

(

[instance] => 2

)

)