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

WBOY
WBOYOriginal
2016-06-13 13:18:531185Durchsuche

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。

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