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PHP中的Magic Method

Jun 23, 2016 pm 02:30 PM

1. __construct()和__destruct()

  在实例被 创建/销毁 的时候被调用,都可以传递0个或多个参数。

  class A  {    function A()    {      echo "build A";    }    function __destruct()    {      echo "destroy A";    }  }  $obj = new A();  //unset($obj); 
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  Note:The destructor method will be called as soon as there are no other references to a particular object, or in any order during the shutdown sequence.

  关于构造函数,PHP5.3.3开始,一个定义在某个特定的命名空间里的class中以类名命名的方法将不再被认为是构造函数。在无命名空间的类中与原来一样依旧是构造函数。如:

namespace Foo;class Bar {    public function Bar() {        // treated as constructor in PHP 5.3.0-5.3.2        // treated as regular method as of PHP 5.3.3    }}
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  如果没有namespace Foo; 那么Bar()还将被当作构造函数。另外,如果存在下面的情况:

  function __construct()    {      echo "construct A";    }    function A()    {      echo "build A";    }    function __destruct()    {      echo "destroy A";    }  }
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  即既包含__construct()又包含与类名同名的函数,那么将只调用__construct()。

2. __call()和__callStatic()

  当尝试调用一个不存在的方法时调用该方法。两个参数,一个是方法名,一个是被调用方法的参数数组。

class MethodTest{    public function __call($name, $arguments)    {        // Note: value of $name is case sensitive.        echo "Calling object method '$name' "             . implode(' ', $arguments). "<br>";    }    public static function __callStatic($name, $arguments)    {        // Note: value of $name is case sensitive.        echo "Calling static method '$name' "             . implode(' ', $arguments). "<br>";    }}$obj = new MethodTest;$obj->runTest('in','object','context');MethodTest::runTest('in','static','context'); 
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  其中,$arguments作为一个array传入。运行结果:

Calling object method 'runTest' in object contextCalling static method 'runTest' in static context
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  还要注意函数的作用域protected和private:

class TestMagicCallMethod {    public function foo()    {        echo __METHOD__.PHP_EOL."<br>";    }    public function __call($method, $args)    {        echo __METHOD__.PHP_EOL."<br>";        if(method_exists($this, $method))        {            $this->$method();        }    }       protected function bar()    {        echo __METHOD__.PHP_EOL."<br>";    }    private function baz()    {        echo __METHOD__.PHP_EOL."<br>";    }}$test    =    new TestMagicCallMethod();$test->foo();/** * Outputs: * TestMagicCallMethod::foo */$test->bar();/** * Outputs: * TestMagicCallMethod::__call * TestMagicCallMethod::bar */$test->baz();/** * Outputs: * TestMagicCallMethod::__call * TestMagicCallMethod::baz */
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3.__get()和__set()

  当试图读取一个对象并不存在的属性的时候被调用。

  Note:我们可以用这个函数实现类似java中反射的各种操作。

class Test{   public function __get($key)   {      echo $key . " not exists";   }   public function __set($key,$value)   {      echo $key . " = ".$value;   }}$t = new Test();echo $t->name."<br>";$t->name = "abc";输出:name not existsname = abc
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4. __toString()

  这个方法类似于java的toString()方法,当我们直接打印对象的时候回调用这个函数,函数必须返回一个string。

class Test{    private $name = "abc";    private $age = 12;    public function __toString()    {        return "name : $this->name, age : $this->age";    }}$t = new Test();echo $t;输出:name : abc, age : 12
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 还有__isset(), __unset(), __sleep(), __wakeup(), __toString(), __invoke(), __set_state() and __clone()就不一一赘述。

 

 

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