PHP 5.0对象模型深度探索之绑定

class father
{
protected $salutation = "hello there!"; //问候

public function getsalutation()
{
print("$this-＞salutationn");
$this-＞identify();
}

protected function identify()
{
print("i am father.
n");
}
};

class son extends father
{
protected $salutation = "hey!"; //父类中的protected $salutation 被覆写

protected function identify() //父类中的protected identify() 被覆写
{
print("i am son.
n");
}
};

$obj = new son();
$obj-＞getsalutation(); //输出hey! i am son.
?＞

//注: 在子类中没有覆写getsalutation()，但实际上仍然存在一个getsalutation().这个类中的$salutation和identify()
//与son子类的实例中的getsalutation()方法动态绑定，所以调用son的实例的getsalutation()方法，
//将调用son类中的成员salutation及identify()，而不是父类中的成员salutation及identify().

class father
{
private $salutation = "hello there!";

public function getsalutation()
{
print("$this-＞salutationn");
$this-＞identify();
}

private function identify()
{
print("i am father.
n");
}
}

class son extends father
{
private $salutation = "hey!";
private function identify()
{
print("i am son.
n");
}
}

$obj = new son();
$obj-＞getsalutation(); //输出hello there! i am father.
?＞

class user //用户
{
protected function isauthorized() //是否是验证用户
{
return(false);
}

public function getname() //获得名字
{
return($this-＞name);
}

public function deleteuser($username) //删除用户
{
if(!$this-＞isauthorized())
{
print("you are not authorized.
n");
return(false);
}

//delete the user
print("user deleted.
n");
}
}

class authorizeduser extends user //认证用户
{
protected function isauthorized() //覆写isauthorized()
{
return(true);
}
}

$user = new user;
$admin = new authorizeduser;

//not authorized
$user-＞deleteuser("zeev");

//authorized
$admin-＞deleteuser("zeev");
?＞