OO PHP 从另一个类访问公共变量
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OO PHP Accessing public variable from another class
提问by Daniel W.
I have a class like the following:
我有一个如下所示的类：
class game {
public $db;
public $check;
public $lang;
public function __construct() {
$this->check = new check();
$this->lang = DEFAULT_LANG;
if (isset($_GET['lang']) && !$this->check->isEmpty($_GET['lang']))
$this->lang = $_GET['lang'];
}
}
As you can see I have a public variable $langthat is also defined via the contructor.
如您所见，我有一个$lang也是通过构造函数定义的公共变量。
The proble is that I want to access the result of this variable from other classes that are not directly related to this class, since I don't want to redeclare it for each different class.
问题是我想从与这个类没有直接关系的其他类访问这个变量的结果，因为我不想为每个不同的类重新声明它。
So for example how can I call the result of that variable from another class, lets call it class Check?
例如，我如何从另一个类调用该变量的结果，让我们调用它class Check？
回答by Daniel W.
if you mark the public $lang;as static:
如果您将其标记public $lang;为静态：
public static $lang;
you can access it via game::$lang;
你可以通过 game::$lang;
if not static, you need to make an instance of game and directly access it:
如果不是静态的，您需要制作一个游戏实例并直接访问它：
$game = new game;
$game->lang;
static call inside of (current) class:
（当前）类内部的静态调用：
self::$lang;
late static boundcall (to inherited static variable):
后期静态绑定调用（对继承的静态变量）：
static::$lang;
call from child class to parent:
从子类调用父类：
parent::$lang;
normal call inside of an instance (instance is when you use new Obj();):
实例内部的正常调用（实例是您使用时new Obj();）：
$this->lang;
BTW:variables defined by define('DEFAULT_LANG', 'en_EN');are GLOBAL scope, mean, can access everywhere!
顺便说一句：定义的变量define('DEFAULT_LANG', 'en_EN');是全局范围的，意思是，到处都可以访问！
<?php
define('TEST', 'xxx');
class game {
public function __construct() {
echo TEST;
}
}
//prints 'xxx'
new game;
回答by roy
you can make it static variable, so you will be able to call it anytime anywhere, the diff is that instead of
你可以让它成为静态变量，这样你就可以随时随地调用它，不同之处在于
$this->lang;
when editing it(Works inside class game only) you do :
编辑它时（仅适用于课堂游戏），您可以：
self::$lang;
and when you call/edit it (Works everywhere) from anther class you do :
当你从另一个类调用/编辑它（无处不在）时，你会这样做：
game::$lang
the idea of static class is that its exist only in one instance, so only one $lang exist in your program. but there is no need to load the whole class to get acsess to it.
静态类的思想是它只存在于一个实例中，所以你的程序中只存在一个 $lang 。但是没有必要加载整个类来访问它。
回答by Shoe
How can I call the result of that variable from another class, lets call it class Check?
我如何从另一个类调用该变量的结果，让我们称之为类检查？
A variable doesn't have a result. If you mean to retrieve the state of that variable on a specific object $objof class gamethen you can simply do:
变量没有结果。如果您想在$obj类的特定对象上检索该变量的状态，game那么您可以简单地执行以下操作：
$obj->lang
On a side note if $langis publicly only read only you should protect it by defining it privateor protectedand create a getter methodinstead.
附带说明一下，如果$lang是公开只读的，您应该通过定义它private或protected创建一个getter 方法来保护它。
If you mean that you want to use the same variable name in another class I'd suggest you to consider inheritance:
如果您的意思是要在另一个类中使用相同的变量名，我建议您考虑继承：
class Check extends game { /* now Check has $lang */ }
but the variable of the two objects will be different.
但是两个对象的变量会不同。
回答by Timothy
Since the property is public, you can access it from outside the class as $objInstance->property. It doesn't matter if you're calling it from a function, procedural script, in another object. As long as you have the instance, you can call it's public property. Ex:
由于该属性是公共的，您可以从类外部以$objInstance->property. 如果您从另一个对象中的函数、过程脚本调用它并不重要。只要你有实例，你就可以称它为公共财产。前任：
function foo($c) {
echo $c->lang;
}
foo($check);
Also, some advice on working with objects and such: It's considered better code if you don't create instances of objects in the other objects, but rather pass them in someway (either a setter method or through the constructor). This keeps the classes loosely coupled and results in code that is more reusable and easier to test. So:
此外，关于使用对象等的一些建议：如果您不在其他对象中创建对象的实例，而是以某种方式（通过 setter 方法或通过构造函数）传递它们，则被认为是更好的代码。这使类保持松散耦合，并产生更可重用且更易于测试的代码。所以：
class Game
{
...
public function __construct($check, $defaultLang, $get) {
$this->check = $check;
$this->lang = $defaultLang;
if (isset($get['lang']) && !$this->check->isEmpty($get['lang']))
$this->lang = $get['lang'];
}
...
$game = new Game(new Check(), DEFAULT_LANG, $_GET);
echo $game->check;
The first half of this articleis an accessible explanation of what is known as Dependency Injection.
上半年这篇文章是所谓依赖注入可访问的解释。
