实例详解php中self、parent、this的区别

<?php
/**
* self、parent、this的区别
* by www.jbxue.com
*/
class test{ 
 public $public; 
 private $private; 
 protected $protected; 
 static $instance; 
 static $good = 'tankzhang <br>'; 
 public $tank = 'zhangying <br>'; 
 
 public  function __construct(){ 
 $this->public    = 'public     <br>'; 
 $this->private   = 'private    <br>'; 
 $this->protected = 'protected  <br>'; 
 
 } 
 public 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; 
 } 
 static function sta_function(){ 
 echo "you request static function<br>"; 
 } 
} 
 
class test1 extends test{ 
 
 static $love = "tank <br>"; 
 private $aaaaaaa = "ying <br>"; 
 
 public function __construct(){ 
 parent::tank(); 
 parent::__construct(); 
 } 
 public function tank(){ 
 echo $this->public; 
 echo $this->protected; 
 echo $this->aaaaaaa; 
 $this->pro_function(); 
 } 
 
 public  function test1_function(){ 
 echo self::$love; 
 echo self::$good; 
 echo parent::$good; 
 echo parent::$tank;   //Fatal error: Access to undeclared static property: test::$tank 
 echo self::$tank;     //Fatal error: Access to undeclared static property: test::$tank 
 } 
 static function extends_function(){ 
 parent::sta_function(); 
 self::pro_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，会调用子类中的方法。 
test1::test1_function(); 
test1::extends_function();  //执行一部分后，报Fatal error: Using $this when not in object context in D:\xampp\htdocs\mytest\www4.php on line 32 
?>