<?php 
class FileRead
{
 protected $handle = NULL;

 function __construct(){
  $this->handle = fopen(...);
 }

 function __destruct(){
  fclose($this->handle);
 }
}
?>

<?php 
class TmpFileRead extends FileRead
{
 function __construct(){
  parent::__construct();
 }

 function __destruct(){
  parent::__destruct();
 }
}
?>

<?php
class MethodTest 
{
 public function __call ($name, $arguments) {
  echo "Calling object method '$name' ". implode(', ', $arguments). "\n";
 }

 public static function __callStatic ($name, $arguments) {
  echo "Calling static method '$name' ". implode(', ', $arguments). "\n";
 }
}

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

<?php 
class MethodTest
{
 private $data = array();

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

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

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

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

<?php
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();
 }
}
?>

<?php
// Declare a simple class
class TestClass
{
 public function __toString() {
  return 'this is a object';
 }
}

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

<?php
class CallableClass 
{
 function __invoke() {
  echo 'this is a object';
 }
}
$obj = new CallableClass;
var_dump(is_callable($obj));
?>

<?php
class A
{
 public $var1;
 public $var2;

 public static function __set_state ($an_array) {
  $obj = new A;
  $obj->var1 = $an_array['var1'];
  $obj->var2 = $an_array['var2'];
  return $obj;
 }
}

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

<?php 
public 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.' . E_USER_ERROR);
 }
}
?>