php - 重用 php 类变量

Question

class Human{
    private $name = 'Foobar';
    private $nick_name = 'King Foobar';
}

我想这样写；

class Human{
    private $name = 'Foobar';
    private $nick_name = 'King '.$this->name; // doesn't work, ignore the . error
    private $nick_name = 'King '.$name; // doesn't work, ignore the . error
}

但是，PHP 会报错。有没有办法绕过它？
我知道这在 Python 中是可能的

class Human:
        name = 'Foobar'
        nick_name = 'King '+name

a = Human()
print(a.nick_name)

Answer 1

你不能像你声明的那样做 $this->name 因为 $this 还没有初始化。

但是，您可以在构造函数中执行此操作以实现您想要的。

class Human{
    private $name;
    private $nick_name;

    public function __construct(){
        $this->name = "Foobar";
        $this->nick_name = "King " . $this->name;
    }
}

如果您愿意，您还可以向构造函数添加可选参数...

public function __construct($name = "Foobar", $nickname = NULL){
    $this->name = $name;

    // If the nickname is null, it will be King and the name
    // Otherwise it will be the nickname passed in the parameter
    $this->nick_name = $nickname ? $nickname : ("King " . $this->name);
}

结果是:

$humanA = new Human(); // Name: Foobar && Nickname: King Foobar
$humanB = new Human('MyName'); // Name: MyName && Nickname: King MyName
$humanC = new Human('MyName', 'MyNickname'); // Name: MyName && Nickname: MyNickname