一，public,private,protected的区别
public:权限是最大的，可以内部调用，实例调用等。
protected: 受保护类型，用于本类和继承类调用。
private: 私有类型，只有在本类中使用。
二，实例
<?phperror_reporting(E_ALL);class test{ public $public; private $private; protected $protected; static $instance; public function __construct(){ $this->public = 'public <br>'; $this->private = 'private <br>'; $this->protected = 'protected <br>'; } static function tank(){ if (!isset(self::$instance[get_class()])) { $c = get_class(); self::$instance = new $c; } return self::$instance; } public function pub_function() { echo "you request public function<br>"; echo $this->public; echo $this->private; //private,内部可以调用 echo $this->protected; //protected,内部可以调用 $this->pri_function(); //private方法，内部可以调用 $this->pro_function(); //protected方法，内部可以调用 } protected function pro_function(){ echo "you request protected function<br>"; } private function pri_function(){ echo "you request private function<br>"; }}$test = test::tank();echo $test->public;echo $test->private; //Fatal error: Cannot access private property test::$privateecho $test->protected; //Fatal error: Cannot access protected property test::$protected$test->pub_function();$test->pro_function(); //Fatal error: Call to protected method test::pro_function() from context$test->pri_function(); //Fatal error: Call to private method test::pri_function() from context?>从上面的例子中，我们可以看出，
public:??? 可以class内部调用，可以实例化调用。
private:?? 可以class内部调用，实例化调用报错。
protected：? 可以class内部调用，实例化调用报错。
<?phpclass test{ public $public; private $private; protected $protected; static $instance; public function __construct(){ $this->public = 'public <br>'; $this->private = 'private <br>'; $this->protected = 'protected <br>'; } protected function tank(){ //私有方法不能继承，换成public,protected if (!isset(self::$instance[get_class()])) { $c = get_class(); self::$instance = new $c; } return self::$instance; } public function pub_function() { echo "you request public function<br>"; echo $this->public; } protected function pro_function(){ echo "you request protected function<br>"; echo $this->protected; } private function pri_function(){ echo "you request private function<br>"; echo $this->private; }}class test1 extends test{ public function __construct(){ parent::tank(); parent::__construct(); } public function tank(){ echo $this->public; echo $this->private; //Notice: Undefined property: test1::$private echo $this->protected; $this->pub_function(); $this->pro_function(); $this->pri_function(); //Fatal error: Call to private method test::pri_function() from context 'test1' } public function pro_extends_function(){ echo "you request extends_protected function<br>"; } public function pri_extends_function(){ echo "you request extends_private function<br>"; }}error_reporting(E_ALL);$test = new test1();$test -> tank(); //子类和父类有相同名字的属性和方法，实例化子类时，子类的中的属性和方法会盖掉父类的。?>?从上面的例子中，我们可以看出，
public:??? test中的public可以被继承。
private:?? test中的private不可以被继承。
protected：? test中的protected可以被继承。
static：??????? test中的static可以被继承。
唉，对于这些东西，老是不喜欢记着，用的时候，总感觉不对，又要去查，所以写个例子，方便自己查看。