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
)
)