php class中self,parent,this的区别以及实例介绍
一,this
1,要用this,你必有是一个对像的形势,不然它会报错的,Fatal error: Using $this when not in object context。
2,this可以调用本类中的方法和属性,也可以调用父类中的可以调的方法和属性
二,self
1,self可以访问本类中的静态属性和静态方法,可以访问父类中的静态属性和静态方法。
2,用self时,可以不用实例化的
三,parent
1,parent可以访问父类中的静态属性和静态方法。
2,用parent时,可以不用实例化的
复制代码 代码如下:
class test{
public $public;
private $private;
protected $protected;
static $instance;
static $good = 'tankzhang
';
public $tank = 'zhangying
';
public function __construct(){
$this->public = 'public
';
$this->private = 'private
';
$this->protected = 'protected
';
}
public function tank(){ //私有方法不能继承,换成public,protected
if (!isset(self::$instance[get_class()]))
{
$c = get_class();
self::$instance = new $c;
}
return self::$instance;
}
public function pub_function() {
echo "you request public function
";
echo $this->public;
}
protected function pro_function(){
echo "you request protected function
";
echo $this->protected;
}
private function pri_function(){
echo "you request private function
";
echo $this->private;
}
static function sta_function(){
echo "you request static function
";
}
}
class test1 extends test{
static $love = "tank
";
private $aaaaaaa = "ying
";
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
";
}
}
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 $this when not in object context in D:\xampp\htdocs\mytest\www4.php on line 32
?>
1,当我们调用$test->tank(); 这个方法时,tank里面的$this是一个对像 ,这个对像可以调用本类,父类中的方法和属性,
2,test1::test1_function(); 当我们用静态的方法去调用非静态方法时,会显示警告的,Non-static method test::test1_function() should not be called statically可以看出不,self可以调用本类,父类中的静态属性 ,parent可以调用父类中的静态属性 ,二者调用非静态属性会报错。代码中有注释
3,test1::extends_function(); 这一步会报错,报在非对像中使用$this 。为什么会这样呢,test1::extends_function();只是调用了class中的一个方法,并没有实例化,所以根本不存在什么对像,当父类中用到$this时,就会报错

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