magische Methode in PHP

__construct()，类的构造函数
__destruct()，类的析构函数
__call()，在对象中调用一个不可访问方法(私有或者不存在)时调用
__callStatic()，用静态方式中调用一个不可访问方法时调用
__get()，获得一个类的成员变量时调用
__set()，设置一个类的成员变量时调用
__isset()，当对不可访问属性调用isset()或empty()时调用
__unset()，当对不可访问属性调用unset()时被调用。
__sleep()，执行serialize()时，先会调用这个函数
__wakeup()，执行unserialize()时，先会调用这个函数
__toString()，类被当成字符串时的回应方法
__invoke()，调用函数的方式调用一个对象时的回应方法
__set_state()，调用var_export()导出类时，此静态方法会被调用。
__clone()，当对象复制完成时调用

<?php &#160;
class ConDes
{
&#160;&#160;&#160; protected $a = &#39;&#39;;

&#160;&#160;&#160; function __construct(){
&#160;&#160;&#160;&#160;&#160;&#160;&#160; echo &#39;在构造函数中<br>';
    }

    function __destruct(){

        echo '在析构函数中<br>';
    }
}

$val = new ConDes();
unset($val);

?><pre name="code" class="php">

<?php  
class MethodTest  
{
    public function __call ($name, $arguments) {
    var_dump($arguments);
        echo "object method $name and ".implode(',',$arguments)."<br>";
    }

    public static function __callStatic ($name, $arguments) {
        echo "static method $name and ".implode(',',$arguments)."<br>";
    }
}

$obj = new MethodTest;
$obj->runTest('in object context','another arg');
MethodTest::runTest('in static context');  
?>

<?php
class MethodTest  
{
    private $data = array();
    private $a = &#39;&#39;;
    public $bbb = &#39;&#39;;

    public function __set($name, $value){
        $this->data[$name] = $value;
		echo '__set';
		var_dump($this->data);
    }

    public function __get($name){
		echo '__get';
		var_dump($this->data);
        if(array_key_exists($name, $this->data))
            return $this->data[$name];
        return NULL;
    }

    public function __isset($name){
		echo '__isset';
        return isset($this->data[$name]);
    }

    public function __unset($name){
		echo '__unset';
        unset($this->data[$name]);
    }
}

$in = new MethodTest();
$in->a = 'aaaa';
$aaa = $in->a;
$res = isset($in->c)? 'set':'not set';
echo '<br>'.$res.'<br>';
unset($in->a);
?>

<?php
class Connection {
&#160;&#160;&#160; public $link;
&#160;&#160;&#160; private $server, $username, $password, $db;
&#160;&#160; &#160;
&#160;&#160;&#160; public function __construct($server, $username, $password, $db)
&#160;&#160;&#160; {
&#160;&#160;&#160;&#160;&#160;&#160;&#160; $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()
    {
    echo 'sleep<br>';
        return array('server', 'username', 'password', 'db');
    }
    
    public function __wakeup()
    {
    echo 'wakeup<br>';
        $this->connect();
    }
}


$a = new Connection('localhost','mosi','moshi','test');
$sql = 'select id,username from user limit 1';
$res = mysql_query($sql,$a->link);
$res = mysql_fetch_array($res);
var_dump($res);

$sres = serialize($a);
mysql_close($a->link);
//unset($a);

$unsres = unserialize($sres);
var_dump($unsres);
$sql = 'select id,username from user limit 1';
$ress = mysql_query($sql,$unsres->link);
$ress = mysql_fetch_array($ress);
var_dump($ress);


?>

<?php  
class TestClass  
{
    public function __toString() {
        return &#39;this is a object&#39;;
    }
}

$class = new TestClass();
echo $class;  
?>

<?php
class Invoke{
	public function __invoke(){
		echo 'in invoke<br>';
	}
}

class noInvoke{

}

$obj = new Invoke();
$obj();

var_dump(is_callable($obj));

$obj2 = new noInvoke();
//$obj2();
var_dump(is_callable($obj2));

<?php  
class A  
{
    public $var1;
    public $var2;
	public static function __set_state ($arr) {
        $obj = new A;
        $obj->var1 = 'var11';
        $obj->var2 = $arr['var2'];
        return $obj;
    }
}

$a = new A;
$a->var1 = 5;
$a->var2 = 'foo';
var_dump($a);  
var_export($a);  

eval('$ress = '.var_export($a,true).';');
var_dump($ress);

?>

<?php  
class Singleton {  
    private static $_instance = NULL;

    // 私有构造方法 
    private function __construct() {}

    public static function getInstance() {
        if (is_null(self::$_instance)) {
            self::$_instance = new Singleton();
        }
        return self::$_instance;
    }

    // 防止克隆实例
    public function __clone(){
        die('Clone is not allowed error: ' . E_USER_ERROR);
    }
}


$a = Singleton::getInstance();
$b = Singleton::getInstance();

if( $a === $b ){
	echo 'equal<br>';
}

$c = clone $b;
?>