PHP Access公共变量从子类收缩

Question

How can I access a public property in Child class that was set by a Parent class with __construct?

For example:

class Parent
{
    protected $pVariableParent = 'no info'; //This have to be set for all classes

    public function __construct()
    {
        $this->setPVariable(); //Changing the property when class created.
    }

    public function setPVariable(){
        $this->pVariableParent = '123';
    }
}

Class Child extends Parent
{
    public function __construct()
    {
        if(isset($_GET['info']){
            echo $this->pVariableParent;
        }
    }
}

$pInit = new Parent;
$cInit = new Child;

In this state the request site.php/?info shows no info . But if I call $this->setPVariable(); from Child, everything works and shows 123 . Why I can't access already changed property from Parent? Is it because when I call the Child class it just reads the properties and methods of all parents but doesn't trigger any construct functions? And what is the best way to do it? Thanx.

Answer 1

The problem is that you overrode the parent constructor, so setPVariable is not called in the child constructor.

To extend the parent constructor instead of override:

Class Child extends Parent
{
  public function __construct()
    {
      parent::__construct();
      if(isset($_GET['info']){
        echo $this->pVariableParent;
    }
  }
}

http://php.net/manual/it/keyword.parent.php

Let me try to clarify one point:

Why I can't access already changed property from Parent?

Because the property is not already changed. You are creating two separate objects; $pInit is an instance of the parent class and its property value gets changed in the constructor. $cInit is an instance of the child class and its property value is unchanged since you override the constructor and the child class does not change the property value. $pInit and $cInit are not related (except by type), and they certainly don't influence the internal structure of each other.