<?php
 class A {
   public $foo = 1;
 } 
 
 $a = new A;
 $b = $a;   // $a ,$b都是同一个标识符的拷贝
       // ($a) = ($b) = <id>
 $b->foo = 2;
 echo $a->foo."\n";//2

 $c = new A;
 $d = &$c;  // $c ,$d是引用
       // ($c,$d) = <id>
 
 $d->foo = 2;
 echo $c->foo."\n";//2
 
 $e = new A;
 
 function foo($obj) {
   // ($obj) = ($e) = <id>
   $obj->foo = 2;
 }
 
 foo($e);
 echo $e->foo."\n";//2

 <?php
 class 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()
   {
     // 强制复制一份this->object， 否则仍然指向同一个对象
     $this->object1 = clone $this->object1;
   }
   
   function cloneTest()
   {
     echo 'cloneTest';
   }
 }
 
 $obj = new MyCloneable();
 
 $obj->object1 = new SubObject();
 $obj->object2 = new SubObject();
 
 $obj2 = clone $obj;
 
 print("Original Object:\n");
 print_r($obj);
 
 print("Cloned Object:\n");
 print_r($obj2);
 echo $obj2->cloneTest().":\n";
 echo (new Reflectionclass($obj2));

Original Object:
MyCloneable Object
(
  [object1] => SubObject Object
    (
      [instance] => 1
    )

  [object2] => SubObject Object
    (
      [instance] => 2
    )

)
Cloned Object:
MyCloneable Object
(
  [object1] => SubObject Object
    (
      [instance] => 3
    )

  [object2] => SubObject Object
    (
      [instance] => 2
    )

)
cloneTest:
Class [ <user> class MyCloneable ] {
 @@ /public/t.php 18-33

 - Constants [0] {
 }

 - Static properties [0] {
 }

 - Static methods [0] {
 }

 - Properties [2] {
  Property [ <default> public $object1 ]
  Property [ <default> public $object2 ]
 }

 - Methods [2] {
  Method [ <user> public method __clone ] {
   @@ /public/t.php 23 - 27
  }

  Method [ <user> public method cloneTest ] {
   @@ /public/t.php 29 - 32
  }
 }
}

 class Foo
 {
   public static $my_static = 'foo';
 
   public function staticValue() {
     return self::$my_static;
   }
 }
 
 class Bar extends Foo
 {
   public function fooStatic() {
     return parent::$my_static;
   }
 }
 
 
 print Foo::$my_static . "\n";
 
 $foo = new Foo();
 print $foo->staticValue() . "\n";
 print $foo->my_static . "\n";   // Undefined "Property" my_static 
 
 print $foo::$my_static . "\n";
 $classname = 'Foo';
 print $classname::$my_static . "\n"; // As of PHP 5.3.0
 
 print Bar::$my_static . "\n";
 $bar = new Bar();
 print $bar->fooStatic() . "\n";

 <?php
 class A
 {
   
   private $proPrivate = "private of A";
   protected $proProtected = "protected of A";
   public $proPublic = "public of A";
   
   private function foo()
   {
     echo $this->proPrivate."\n";
     echo $this->proProtected."\n";
     echo $this->proPublic."\n";
   }
   
   public function test()
   {
     $this->foo();
     static::foo();
   }
 }
 
 class B extends A
 {
  /* foo() will be copied to B, hence its scope will still be A and
   * the call be successful */
 }
 
 class C extends A
 {
   private $proPrivate = "private of C";
   protected $proProtected = "protected of C";
   public $proPublic = "public of C";
   
   private function foo()
   {
     /* original method is replaced; the scope of the new one is C */
     echo "I am C\n";
   }
   
   public function myFoo()
   {
     //parent::foo();
     $this->foo();
   }
 }
 
 echo "Class B:\n";
 $b = new B();
 $b->test();
 echo "\nClass C:\n";
 $c = new C();
 $c->myFoo();
 $c->test();  //fails

Class B:
private of A
protected of A
public of A
private of A
protected of A
public of A

Class C:
I am C
private of A
protected of C
public of C 
Fatal error: Uncaught Error: Call to private method C::foo() from context 'A' in /public/t.php:19 Stack trace: #0 /public/t.php(54): A->test() #1 {main} thrown in /public/t.php on line 19