如何访问私有变量？

Question

This is my class

abstract class DataStore_Adapter {

    private $id;

    abstract function update();
    abstract function insert();

    function __construct() {
        $this-> id = 3;
    }
    function save() {
        if(! is_null($this->id)) {
            $this->update();
        } else {
            $this->insert();
        }
    }
}

class VS_DataStroe_Adapter extends DataStore_Adapter {

    function __construct() {
        parent:: save();
    }
    function update() {
        echo "successfully updated!";
    }
    function insert() {
        echo "successfully inserted!";
    }
}

$vs_data = new VS_DataStroe_Adapter();

Running this code i get the result

successfully inserted!

and if i remove

$this-> id = 3;

from the constructor method of DataStore_Adapter and place it inside function save() it gives me result;

successfully updated!

I need a clarification on this behavior. As i have declared $id as a private variable , i know its only can be access through DataStore_Adapter class. But when i initialize it inside save() method sub-class can access its value.. How this is possible? and why?

Answer 1

Private attribute is accessible only in the scope of the class which declares it. Save() is defined in the parent class (which declares ID) so it can access it.

In other words private DataStore_Adapter::$id can be accessed by DataStore_Adapter::save() because both are defined in the same class. If you want to share attributes or methods through inheritance you can use protected.