在PHP中使用“this”和“self”

Use $this to refer to the current object. Use self to refer to the
current class. In other words,use $this->member for non-static
members,use self::$member for static members.

http://board.phpbuilder.com/showthread.php?10354489-RESOLVED-php-class-quot-this-quot-or-quot-self-quot-keyword

class Demo
{
    private static $name;
    private $age;

    public function __construct($name,$age) 
    {
        self::$name = $name;
        $this->age=$age;
    }   

    public function show()
    {       
        echo "Name : ",self::$name,"<br/>";   //Accessing by self
        echo "Name : ",Demo::$name,"<br/>";   //Accessing by class name 
        echo "Age  : ",$this->age,"<br/>";    
    } 
}

$demo = new Demo("Tiny",13);
$demo->show();

这会产生以下输出.

Name : Tiny
Name : Tiny
Age : 13

前面代码段中self :: $name和Demo :: $name有什么区别？

class Person1
{
    private $name;
    private $address;

    public function __construct($name,$address)
    {
        $this->name = $name;
        $this->address = $address;
    }

    public function show()
    {
        echo "Name    : ",$this->name,"<br/>";    
        echo "Address : ",$this->address,"<br/>";  //Accessing by this
    }
}

$p1=new Person1("xxx","yyy");
$p1->show();

class Person2
{
    private $name;
    private $address;

    public function __construct($name,$address)
    {
        self::$name = $name;
        self::$address = $address;
    }

    public function show()
    {
        echo "Name    : ",self::$address,"<br/>"; //Accessing by self 
    }
}

$p2=new Person1("xxx","yyy");
$p2->show();

在前面的两个类Person1和Person2产生如下相同的输出.

Name : xxx
Address : yyy

有什么区别(如在Preson1类中,show()方法)

$this->name;
$this->address;

和(如在Preson2类中,show()方法)

self::$name;
self::$address;

在这种背景下？