php class中public,private,protected的区别,以及实例
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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
- <?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。
- <?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。
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