php class中public,private,protected的区别，以及实例

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

查看复制打印?

<?php

error_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 $test->private; //Fatal error: Cannot access private property test::$private

echo $test->protected; //Fatal error: Cannot access protected property test::$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。

查看复制打印?

<?php

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>';

}

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。