php面向对象访问控制public,private,protected详解_PHP教程

error_reporting(E_ALL);

class test{

public $public;

private $private;

protected $protected;

static $instance;

public function __construct(){

$this->public = 'public
';

$this->private = 'private
';

$this->protected = 'protected
';

}

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
";

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
";

}

private function pri_function(){

echo "you request private function
";

}

}

$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

?>

public = 'public
'; $this->private = 'private
'; $this->protected = 'protected
'; } static function tank(){ if (!isset(self::$instance[get_class()])) { $c = get_class(); self::$instance = new $c; } return self::$instance; } public function pub_function() { echo "you request public function
"; 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
"; } private function pri_function(){ echo "you request private function
"; } } $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。

class test{

public $public;

private $private;

protected $protected;

static $instance;

public function __construct(){

$this->public = 'public
';

$this->private = 'private
';

$this->protected = 'protected
';

}

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
";

echo $this->public;

}

protected function pro_function(){

echo "you request protected function
";

echo $this->protected;

}

private function pri_function(){

echo "you request private function
";

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
";

}

public function pri_extends_function(){

echo "you request extends_private function
";

}

}

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。

?>