php – 覆盖静态变量

发布时间：2020-12-13 21:58:41 所属栏目：PHP教程来源：网络整理

导读：我有两个类(模型和用户),但我有一个问题所以我试图在一个简单的例子中解释它： class person{ protected static $todo ="nothing"; public function __construct(){} public function get_what_todo() { echo self::$todo; }}class student extends person{

我有两个类(模型和用户),但我有一个问题所以我试图在一个简单的例子中解释它：

class person
{
    protected static $todo ="nothing";

    public function __construct(){}

    public function get_what_todo()
    {
        echo self::$todo;
    }
}

class student extends person
{
    protected static $todo ="studing";
}

$s = new student();
$s->get_what_todo(); // this will show the word (nothing)
                     //but I want to show the word (studing)

请给我一个解决方案,但没有在学生班写任何功能我只想在那里做声明:)谢谢:)

解决方法

该原则称为“ late static binding”,并在PHP 5.3.0中引入;使用self关键字访问继承树中调用类中定义的属性,或使用static访问该继承树中子类中定义的属性.

class person
{
    protected static $todo ="nothing";

    public function __construct(){}

    public function get_what_todo()
    {
        echo static::$todo;  // change self:: to static::
    }
}

class student extends person
{
    protected static $todo ="studying";
}

class teacher extends person
{
    protected static $todo ="marking";
}

class guest extends person
{
}

$s = new student();
$s->get_what_todo(); // this will show the "studying" from the instantiated child class

$t = new teacher();
$t->get_what_todo(); // this will show the "marking" from the instantiated child class

$g = new guest();
$g->get_what_todo(); // this will show the "nothing" from the parent class,//    because there is no override in the child class

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!