PHP Codeigniter - parent::__construct
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/17809517/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
PHP Codeigniter - parent::__construct
提问by Seong Lee
When getting inherited from a parent class in PHP, especially in Codeigniter what does parent::__construct or parent::model()do?
当从 PHP 中的父类继承时，尤其是在 Codeigniter 中，它会parent::__construct or parent::model()做什么？
How would it make difference if I don't __constructparent class?
And, which way is suggested?
如果我不上__construct家长课，会有什么不同？而且，建议采用哪种方式？
-Added-
-添加-
The focus is more on Codeigniter specific regarding a call to parent::__constructin different ways depending on versions and also if this could be omitted in case Codeigniter would do this automatically.
重点更多地放在 Codeigniter 特定parent::__construct于根据版本以不同方式调用，以及如果 Codeigniter 会自动执行此操作时是否可以省略。
回答by giorgio
This is a normal class constructor. Let's look at the following example:
这是一个普通的类构造函数。让我们看看下面的例子：
class A {
protected $some_var;
function __construct() {
$this->some_var = 'value added in class A';
}
function echo_some_var() {
echo $this->some_var;
}
}
class B extends A {
function __construct() {
$this->some_var = 'value added in class B';
}
}
$a = new A;
$a->echo_some_var(); // will print out 'value added in class A'
$b = new B;
$b->echo_some_var(); // will print out 'value added in class B'
As you see, class B inherits all values and functions from A. So the class member $some_varis accessible from A as well as from B. Because we've added a constructor in class B, the constructor of class A will NOT be used when you are creating a new object of class B.
如您所见，类 B 继承了 A 的所有值和函数。因此类成员$some_var可以从 A 和 B 访问。因为我们在类 B 中添加了一个构造函数，所以当您使用类 A 的构造函数时，将不会使用它正在创建一个 B 类的新对象。
Now look at the following examples:
现在看看下面的例子：
class C extends A {
// empty
}
$c = new C;
$c->echo_some_var(); // will print out 'value added in class A'
As you can see, because we have not declared a constructor, the constructor of class A is used implicitly. But we can also do the following, which is equivalent to class C:
可以看到，因为我们没有声明构造函数，所以隐式使用了类A的构造函数。但是我们也可以做下面的，相当于C类：
class D extends A {
function __construct() {
parent::__construct();
}
}
$d = new D;
$d->echo_some_var(); // will print out 'value added in class A'
So you only have to use the line parent::__construct();when you want a constructor in the child class to do something, AND execute the parent constructor. Example given:
因此，parent::__construct();当您希望子类中的构造函数执行某些操作并执行父构造函数时，您只需使用该行。给出的例子：
class E extends A {
private $some_other_var;
function __construct() {
// first do something important
$this->some_other_var = 'some other value';
// then execute the parent constructor anyway
parent::__construct();
}
}
More information can be found here: http://php.net/manual/en/language.oop5.php
更多信息可以在这里找到：http: //php.net/manual/en/language.oop5.php
回答by user3274600
what does parent::__construct or parent::model() do?
parent::__construct 或 parent::model() 做什么？
these functions do exactly the same, only the construct function used to be named after the class itself prior to PHP5. I say in your example you are extending the Model class (and on some older version of CI since you don't need to use CI_model), if I'm correct in this __construct is the same as model().
这些函数的作用完全相同，只是构造函数在 PHP5 之前以类本身命名。我在您的示例中说您正在扩展 Model 类（并且在某些旧版本的 CI 上，因为您不需要使用 CI_model），如果我在这个 __construct 中是正确的，则与 model() 相同。
回答by Justin Herrera
It will simply execute the constructor of parent class
它将简单地执行父类的构造函数
