php class中public,private,protected的区别以及实例分析
网络编程 2021-07-05 09:49www.168986.cn编程入门
本篇文章是对php class中public,private,protected的区别以及实例进行了详细的分析介绍,需要的朋友参考下
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 $test->private; //Fatal error: Cannot aess private property test::$private
echo $test->protected; //Fatal error: Cannot aess protected property test::$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。
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
代码如下:
<?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 $test->private; //Fatal error: Cannot aess private property test::$private
echo $test->protected; //Fatal error: Cannot aess protected property test::$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。
代码如下:
<?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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