getting value from a class that instantiated current class

Question

I am really sorry if this is s dumb question and I'm having a brain fart, this just seems like something I should know. If I have a structure similar to below, is there some way to get $fooVar in Class bar. Do I need to find some way to pass $fooVar as a parameter or is there some inheritance there that I can take advantage of? I'd like to avoid passing it as a parameter if at all possible. Class bar extends another class and if I passed t as a parameter I'd have to do some extra work.

Thanks so much for your help.

Class foo{
    $fooVar;
    $bar = new bar()
}//end foo{}
Class bar extends AnotherClass{
    echo $foo->fooVar;
}//end bar{}

Answer 1

First of all I want to say, I just know a bit about php but I think this problem can be adapted to any other OOP based language. So I tried to put some code for you up. Their are 4 different approaches I am aware of. (I want to consider that I didn't test the below code snippets.)

1. Declare a get-Function

in your superclass to access the value of $fooVar. This has the positiv effect to access the value from any other class which can call the get-function.
Like this:

    Class foo{
      private $fooVar;

      function __construct() {
        $bar = new bar();
      }

      function getFooVar() {
        return $fooVar;
      }
    }
    Class bar extends foo{
      function __construct() {
        private $foo = parent::getFooVar(); //init $foo on instantiation by get-function
      }
    }

2.

Declare $fooVar as protected

the make $fooVar only accessible by their subclasses.

    Class foo{
      protected $fooVar;

      function __construct() {
        $bar = new bar();
      }
    }
    Class bar extends foo{
      function __construct() {
        private $foo = parent::$fooVar; //init $foo on instantiation by parent
      }
    }

3. Add $fooVar as parameter

to your subclass constructor. (I am fully aware of that this is not what you want, but I state it here as another solution and for clarification.)

    Class foo{
      protected $fooVar;

      function __construct() {
        $bar = new bar($fooVar);
      }
    }
    Class bar extends foo{
      function __construct($var) {
        private $foo = $var; //init $foo on instantiation with parameter
      }
    }

4.

Make $fooVar global.

(another solution but not recommanded.)

I think you are going well with the get function. From the last two cases I would advice especially against the last one.

I really hope this is what you are looking for and it helps alot.