Heim  >  Artikel  >  Backend-Entwicklung  >  php class中public,private,protected的差异,以及实例

php class中public,private,protected的差异,以及实例

WBOY
WBOYOriginal
2016-06-13 13:18:531208Durchsuche

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

<?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。

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。

Stellungnahme:
Der Inhalt dieses Artikels wird freiwillig von Internetnutzern beigesteuert und das Urheberrecht liegt beim ursprünglichen Autor. Diese Website übernimmt keine entsprechende rechtliche Verantwortung. Wenn Sie Inhalte finden, bei denen der Verdacht eines Plagiats oder einer Rechtsverletzung besteht, wenden Sie sich bitte an admin@php.cn