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What is the special meaning of calling the constructor of an unrelated class in the constructor of PHP?

黄舟
黄舟Original
2017-07-02 09:56:451037browse

I am watching the startup process of Yii2, in which the parent class of Application constructor is written like this; I would like to ask what is special about the last sentence Component::construct($config) being called here Meaning?

    public function construct($config = [])
    {
        Yii::$app = $this;
        $this->setInstance($this);

        $this->state = self::STATE_BEGIN;

        $this->preInit($config);

        $this->registerErrorHandler($config);

        Component::construct($config);
    }

Mainly because there is a problem that I cannot understand in the process of tracking the code,
Component::construct($config)---->Object::construct($config)---> ;Yii::configure($this,$config)
This is how it is handled in Yii::configure:

  public static function configure($object, $properties)
    {
        foreach ($properties as $name => $value) {
            $object->$name = $value;
        }

        return $object;
    }

The corresponding setter function is actually called here, and $config generally contains components, so the setComponents function will be called. This function is defined by the Application parent class, so why can the $this instance call the Application function? $this is obviously an instance of Component, so I can’t understand it. I haven’t learned the basics of PHP well.

application calls the construction method of Component. The construction method of Component inheritsObject classwhere does it call the function of Application

I suddenly remembered that Application extends Module extends ServiceLocator extends Component extends Object, so Component::construct in the constructor of Application is basically calling the constructor of the parent class with multi-layer inheritance. So it can be understood that $this in Object ultimately points to the Application instance.

  public function construct($config = [])
    {
        Yii::$app = $this;
        $this->setInstance($this);

        $this->state = self::STATE_BEGIN;

        $this->preInit($config);

        $this->registerErrorHandler($config);

        Component::construct($config);
    }

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