浅谈PHP的Public、Protected、Private三种方法的区别

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。

<?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 "your 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。

?>

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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浅谈PHP的Public、Protected、Private三种方法的区别

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