初学者的 PHP 类继承

Question

class User{
    public $company_name;
}

class Employer extends User{
    public $fname;
    public $sname;
}

这是我创建的 test.php。我已经包含了类文件。

$employer = new Employer();
$user = new User();
$employer->company_name = "Company name is ";
echo $user->company_name;

当我打印名称时没有任何反应，请告诉我我的代码有什么问题。

Answer 1

您的 Employer 类扩展了您的 User 类，但是当您创建 $user 和 $employer 对象时，它们是独立的实体且不相关。

这样想你的对象:

$employer = new Employer();
// You now have $employer object with the following properties:
// $employer->company_name;
// $employer->fname;
// $employer->sname;

$user = new User();
// You now have $user object with the following properties:
// $user->company_name;

$employer->company_name = "Company name is ";
// You now have $employer object with the following properties:
// $employer->company_name = 'Company name is ';
// $employer->fname;
// $employer->sname;

echo $user->company_name;
// You currently have $user object with the following properties:
// $user->company_name;  /* no value to echo! */

如果你想使用继承的属性，它的工作方式更像这样:

class User{
    public $company_name;

    function PrintCompanyName(){
        echo 'My company name is ' . $this->company_name;
    }
}

class Employer extends User{
    public $fname;
    public $sname;
}

$employer = new Employer();
$employer->company_name = 'Rasta Pasta';
$employer->PrintCompanyName();  //echoes 'My company name is Rasta Pasta.'