• php面向对象类中常用的魔术方法


    1、__construct():构造方法,当类被实例化new $class时被自动调用的方法,在类的继承中可以继承与覆盖该方法,例:

    //__construct()
    class construct{
        public function __construct(){
            $this->var = "this is var";    
        }
    }
    class con2 extends construct{
        public function __construct(){
            $this->var = "this is var2";    
        }
    }
    $con2 = new con2;
    echo $con2->var;

    3、__destruct():当对象销毁或者不再使用时(页面运行完),自动调用这个方法,例:

    class construct{
        public function __construct(){
            $this->var = "this is var";    
        }
        public function __destruct(){
            echo 'close';    
        }
    }
    $con = new construct;
    //或者最常用的关闭资源
    class destruct{
        public function __construct(){
            $this->logfile_handle = fopen('/tmp/log.txt',w);    
        }
        public function __destruct(){
            fclose($this->logfile_handle);    
        }
    }

    4、__toString():该方法用于一个类被当成字符串时应怎么样回应,也就是echo $class时返回的内容是什么,如果没有__toString()魔术方法时,将会返回一个E_RECOVERABLE_ERROR级别的致命错误。

    例:

    <?php
    class TestClass{
        public $foo;
        public function __construct($foo){
            $this->foo = $foo;    
        }
        public function __toString(){
            return $this->foo;
        }
        
    }
    $class = new TestClass('Hello');
    echo $class;//Hello
    ?>

    5、__invoke():该魔术方法用于类被当作函数使用时,自动调用该方法,但是...__invoke()魔术方法只在PHP5.3.0以上才有效;例

    //__invoke() PHP5.3.0以上版本有效
    class CallableClass{
        function __invoke($x){
            var_dump($x);    
        }
    }
    $obj = new CallableClass;
    $obj(5);
    var_dump(is_callable($obj));//true

    6、__get()与__set():从一个难以访问的属性读取数据是自动调用__get()魔术方法,从一个难以访问的熟悉赋值的时候自动调用__set()魔术方法,难以访问包括(私有属性,未定义属性、没有初始化的属性)例:

    //__get()  __set()
    class demoClass{
        private $a;
        private function __get($name){
            return 'this var not exist';
        }
        private function __set($name,$value){
            echo 'this var value not exist';    
        }
    }
    $demo = new demoClass();
    var_dump($demo->a);//调用__get()方法
    $demo->a = 1;//调用__set()方法

    7、__call():该方法在范围类中不存在的方法时自动调用的方法,参数有两个;例:

    //__call()
    class funClass{
        public function __call($name,$arg){
            echo $name.'function not exist';    
        }
    }
    $fun = new funClass();
    $fun->aa();//function not exist

    8、__sleep()和__wakeup:这两个魔术方法是在对象序列化serialize()和解序列化unserialize()自动调用的方法:例

    //__sleep __wakeup 简单实例
    class sleepClass{
        public $myContent;
        public function __construct($string){
            $this->myContent = $string;    
        }
        public function __sleep(){
            $this->myContent = "this is mimi";
            return array('myContent');
        }
        public function __wakeup(){
            echo 'aaa';    
        }
    }
    $sleep = new sleepClass('i love bb');
    $ser = serialize($sleep);//this is mimi
    unserialize($ser);//aaa
    //或者 常用实例
    class Connection {
        protected $link;
        private $server, $username, $password, $db;
        public function __construct($server, $username, $password, $db)
        {
            $this->server = $server;
            $this->username = $username;
            $this->password = $password;
            $this->db = $db;
            $this->connect();
        }
        private function connect()
        {
            $this->link = mysql_connect($this->server, $this->username, $this->password);
            mysql_select_db($this->db, $this->link);
        }
        public function __sleep()
        {
            return array('server', 'username', 'password', 'db');
        }
        public function __wakeup()
        {
            $this->connect();
        }
    }
    $con = new Connection('127.0.0.1','root','','mythinkcom');
    echo serialize($con);

    9、__clone():$obj2 = clone $obj1与$obj2 = $obj1的区别是前者有两块内存地址,而后者只有一块内存地址。

    class cloneClass{
        public $var = 'aa';    
    }
    $clone = new cloneClass;
    $clone2 = clone $clone;
    echo $clone->var;
    echo $clone2->var;
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  • 原文地址:https://www.cnblogs.com/longfeiPHP/p/4987928.html