php class中public,private,protected的区别以及实例分析

复制代码 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 $test->private; //Fatal error: Cannot access private property test::$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
?>

复制代码 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。
?>