PHP中魔术方法的用法
发布日期:2021-06-30 19:32:55
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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。 * */// __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"; /** 输出结果如下: __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;$obj->runTest('in object context', 'param2', 'param3');//MethodTest::runTest('in static context'); // As of PHP 5.3.0echo "\n\n"; /** 输出结果如下: __call, Calling object method 'runTest' in object context, param2, param3 string(10) "__invoke: " */// __invoke/* The __invoke method is called when a script tries to call an object as a function. Note: This feature is available since PHP 5.3.0.*/class CallableClass { function __invoke($x) { var_dump($x); }}$obj = new CallableClass;//$obj(5);var_dump('__invoke: ' . is_callable($obj));echo "\n\n"; // __sleep __wakeup/* 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IDprint_r($u);print_r($u2);echo "\n\n"; /** 输出结果如下: __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"; /** 输出结果如下: __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";/** 输出结果如下: __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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