PHP中魔術方法的用法

/** PHP把所有以__（兩個下劃線）開頭的類方法當成魔術方法。所以你定義自己的類方法時，不要以 __為前綴。 * */// __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"; 
/**輸出結(jié)果如下：__toString, Hello__set, Setting 'a' to '1'__get, Getting 'a'__isset, Is 'a' set?bool(true)__unset, Unsetting 'a'__isset, Is 'a' set?bool(false)**/// __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;
$obj->runTest('in object context', 'param2', 'param3');
//MethodTest::runTest('in static context'); // As of PHP 5.3.0
echo "\n\n"; 
/**輸出結(jié)果如下：__call, Calling object method 'runTest' in object context, param2, param3string(10) "__invoke: "*/// __invoke
/* The __invoke method is called when a script tries to call an object as a function.Note: This feature is available since PHP 5.3.0.
*/
class CallableClass {function __invoke($x) {var_dump($x);}
}$obj = new CallableClass;
//$obj(5);
var_dump('__invoke: ' . is_callable($obj));
echo "\n\n"; // __sleep  __wakeup
/*串行化serialize可以把變量包括對象,轉(zhuǎn)化成連續(xù)bytes數(shù)據(jù). 你可以將串行化后的變量存在一個文件里或在網(wǎng)絡上傳輸. 然后再反串行化還原為原來的數(shù)據(jù). 你在反串行化類的對象之前定義的類,PHP可以成功地存儲其對象的屬性和方法. 有時你可能需要一個對象在反串行化后立即執(zhí)行. 為了這樣的目的,PHP會自動尋找__sleep和__wakeup方法.當一個對象被串行化,PHP會調(diào)用__sleep方法(如果存在的話). 在反串行化一個對象后,PHP 會調(diào)用__wakeup方法. 這兩個方法都不接受參數(shù). __sleep方法必須返回一個數(shù)組,包含需要串行化的屬性. PHP會拋棄其它屬性的值. 如果沒有__sleep方法,PHP將保存所有屬性.下面的例子顯示了如何用__sleep和__wakeup方法來串行化一個對象. Id屬性是一個不打算保留在對象中的臨時屬性. __sleep方法保證在串行化的對象中不包含id屬性. 當反串行化一個User對象,__wakeup方法建立id屬性的新值. 這個例子被設計成自我保持. 在實際開發(fā)中,你可能發(fā)現(xiàn)包含資源(如圖像或數(shù)據(jù)流)的對象需要這些方法*/class User {public $name;public $id;function __construct() {//give user a unique ID 賦予一個差別 的ID$this->id = uniqid();}//__sleep返回值的類型是數(shù)組，數(shù)組中的值是不需要串型化的字段idfunction __sleep() {//do not serialize this->id 不串行化idreturn(array("name"));}function __wakeup() {//give user a unique ID$this->id = uniqid();}}//create object 成立一個器材
$u = new User;
$u->name = "Leon"; //serialize it 串行化 留意不串行化id屬性,id的值被遺棄
$s = serialize($u);
echo "__sleep, __wakeup, s: $s"; //unserialize it 反串行化 id被重新賦值
$u2 = unserialize($s); //$u and $u2 have different IDs $u和$u2有差別 的ID
print_r($u);
print_r($u2);
echo "\n\n"; 
/**輸出結(jié)果如下：__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
/*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//$an_array打印出來是數(shù)組，而不是調(diào)用時傳遞的對象print_r($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"; 
/**輸出結(jié)果如下：__set_state:Array([var1] => 5[var2] => foo)object(A)#5 (2) {["var1"]=>int(5)["var2"]=>string(3) "foo"}*/// __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";
/**輸出結(jié)果如下：__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)) */

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