类的方法中的未定义变量

类的方法中的未定义变量 - PHP(Undefined variable in a method of a class - PHP)

我想知道为什么我的下面的代码不起作用。 它给了我这个错误：

（！）注意：未定义的变量：第8行的C：\ wamp \ www \ oops \ visibility-levels \ public.php中的uname

<?php class User { public $uname = "admin"; public function setUsername() { $this->uname = $uname; } public function getUsername() { return $this->uname; } } $user = new User(); $user->setUsername(); echo $user->getUsername(); ?>

但是当我将上面的代码修改为 -

<?php class User { public $uname; public function setUsername($uname) { $this->uname = $uname; } public function getUsername() { return $this->uname; } } $user = new User(); $user->setUsername("admin"); echo $user->getUsername(); ?>

然后它工作正常，并给我以下输出 -

管理

但我不明白为什么我在我的第一段代码中得到了未定义的变量uname。 任何的想法？

I would like to know why my following code doesn't work. It is giving me this error:

( ! ) Notice: Undefined variable: uname in C:\wamp\www\oops\visibility-levels\public.php on line 8

<?php class User { public $uname = "admin"; public function setUsername() { $this->uname = $uname; } public function getUsername() { return $this->uname; } } $user = new User(); $user->setUsername(); echo $user->getUsername(); ?>

But when I modify my above code to -

<?php class User { public $uname; public function setUsername($uname) { $this->uname = $uname; } public function getUsername() { return $this->uname; } } $user = new User(); $user->setUsername("admin"); echo $user->getUsername(); ?>

Then it works fine and gives me following output -

admin

But I dont understand why I got undefined variable uname in my first segment of code. Any idea?

最满意答案

因为函数setUserName不知道变量$ uname的值，所以需要在范围内定义它，或者通过函数参数传递。

例如：

public function setUsername() { $uname = 'foo'; $this->uname = $uname; }

将导致输出：foo

because function setUserName doesn't know value of variable $uname, you need to define it inside the scope, or pass via function argument.

for example:

public function setUsername() { $uname = 'foo'; $this->uname = $uname; }

will result in output: foo