PHP: How to call private values of parent construct in child construct?

I 开发者_如何转开发want to be able to set a private attribute's value in the parent constructor, and call the value in a child's constructor or method.

For example:

<?php


abstract class MainClass
{
    private $prop_1;
    private $prop_2;


     function __construct()
     {
            $this->prop_2 = 'this is  the "prop_2" property';
     }
}

class SubClass extends MainClass
{
    function __construct()
    {
        parent::__construct();
        $this->prop_1 = 'this is the "prop_1" property';
    }

    public function GetBothProperties()
    {
        return array($this->prop_1, $this->prop_2);
    }

}

$subclass = new SubClass();
print_r($subclass->GetBothProperties());

?>

Output:

Array
(
    [0] => this is the "prop_1" property
    [1] => 
)

However, if I change prop_2 to protected, the output will be:

Array
(
    [0] => this is the "prop_1" property
    [1] => this is  the "prop_2" property
)

I have basic knowledge of OO and php, but I can't figure out what is preventing prop_2 from being called (or shown?) when it's private; it can't be a private/public/protected issue, since 'prop_1' is private and able to be called and shown... right?

Is it an issue of assigning the values in the child class vs parent class?

I would appreciate help in understanding why.

Thank you.

Private properties of parent class can not be accessed in Child class and vice versa.

You can do like this

abstract class MainClass
{
   private $prop_1;
   private $prop_2;


   function __construct()
   {
        $this->prop_2 = 'this is  the "prop_2" property';
   }

   protected function set($name, $value)
   {
        $this->$name = $value;
   }

   protected function get($name)
   {
      return $this->$name;
   }

 }


class SubClass extends MainClass
{
    function __construct()
    {
        parent::__construct();
        $this->set('prop_1','this is the "prop_1" property');
    }

    public function GetBothProperties()
    {
        return array($this->get('prop_1'), $this->get('prop_2'));
    }

}

If you want to access the parent's properties from the child class, you must make the parent's properties protected NOT private. This way they are still inaccessible externally. You can't override the parent's private properties visibility in the child class in the way you are trying to.

As others have noted, you'd need to change the parent's properties to protected. However, the other way is by implementing a get method for your parent class, which allows you access to the property, or implementing a set method if you want the ability to over-ride it.

So, in your parent class, you'd declare:

protected function setProp1( $val ) {
  $this->prop_1 = $val;
}

protected function getProp1() {
  return $this->prop_1;
}

Then, in your child class, you can access $this->setProp1("someval"); and $val = $this->getProp1(), respectively.

There is a simple trick you an use with lambdas, which I found here: https://www.reddit.com/r/PHP/comments/32x01v/access_private_properties_and_methods_in_php_7/

basically you use a lambda and bind it to the instance and then you can access it's private methods and properties

Info on the lambda call: https://www.php.net/manual/en/closure.call.php