PHP中魔術方法的用法

PHP中魔術方法的用法

/** PHP把所有以__（兩個底線）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 __為首碼。 * */// __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;$obj->runTest('in object context', 'param2', 'param3');//MethodTest::runTest('in static context'); // As of PHP 5.3.0echo "\n\n"; /** 輸出結果如下： __call, Calling object method 'runTest' in object context, param2, param3  string(10) "__invoke: " */// __invoke/*   The __invoke method is called when a script tries to call an object as a function.  Note: This feature is available since PHP 5.3.0.*/class CallableClass {    function __invoke($x) {        var_dump($x);    }}$obj = new CallableClass;//$obj(5);var_dump('__invoke: ' . is_callable($obj));echo "\n\n"; // __sleep  __wakeup/*  序列化serialize可以把變數包括對象,轉化成連續bytes資料. 你可以將序列化後的變數存在一個檔案裡或在網路上傳輸.   然後再反序列化還原為原來的資料. 你在反序列化類的對象之前定義的類,PHP可以成功地儲存其對象的屬性和方法.   有時你可能需要一個對象在反序列化後立即執行. 為了這樣的目的,PHP會自動尋找__sleep和__wakeup方法.  當一個對象被序列化,PHP會調用__sleep方法(如果存在的話). 在反序列化一個對象後,PHP 會調用__wakeup方法.   這兩個方法都不接受參數. __sleep方法必須返回一個數組,包含需要序列化的屬性. PHP會拋棄其它屬性的值.   如果沒有__sleep方法,PHP將儲存所有屬性.下面的例子顯示了如何用__sleep和__wakeup方法來序列化一個對象.   Id屬性是一個不打算保留在對象中的臨時屬性. __sleep方法保證在序列化的對象中不包含id屬性.   當反序列化一個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.   在實際開發中,你可能發現包含資源(像或資料流)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傳回值的類型是數組，數組中的值是不需要串型化的欄位id    function __sleep() {        //do not serialize this->id 不序列化id        return(array("name"));    }    function __wakeup() {        //give user a unique ID        $this->id = uniqid();    }}//create object 成立一個器材$u = new User;$u->name = "Leon"; //serialize it 序列化 留意不序列化id屬性,id的值被遺棄$s = serialize($u);echo "__sleep, __wakeup, s: $s"; //unserialize it 反序列化 id被重新賦值$u2 = unserialize($s); //$u and $u2 have different IDs $u和$u2有差別 的IDprint_r($u);print_r($u2);echo "\n\n"; /** 輸出結果如下：  __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        //$an_array列印出來是數組，而不是調用時傳遞的對象        print_r($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"; /**  輸出結果如下：  __set_state:  Array  (  [var1] => 5  [var2] => foo  )  object(A)#5 (2) {  ["var1"]=>  int(5)  ["var2"]=>  string(3) "foo"  } */// __cloneclass 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  ))  */