Object inheritance, not keeping property

[optikalefx]

I know the problem must be dumb, but this is killing me.  I have 2 classes, one extends another one.  The base class has a variable and later in the code the base class changes that variable.  But after i instantiate the extended class it only has the original value.

 

echo $this->myvar;	// start
$this->myvar = "test ";
echo $this->myvar; // test
require_once("controllers/blog.controller.php");
$blog = new Blog();
echo $blog->myvar;	// start ???????

 

here is app.controller.php

class App {

var $myvar = "start ";
}

 

and here is blog.controller.php

class Blog extends App {

}

 

 

that variable $this->myvar should be the same all the time right? ahhhhhhhhhhh

[trq]

The two instances of the objects aren't related, only there base classes.

[optikalefx]

ok so i wrote that wrong.

 

here is a full php file

 

<?php

class base {
var $myvar = "start";
function changeValue() {
	$this->myvar = "changed";
}
}

class extender extends base {
function showMyvar() {
	echo $this->myvar;
}
}

class extender2 extends base {
function extender2() {
	$this->myvar = "2 changed";
}	
}


$test = new extender;
$test2 = new extender2;	// should change the value
echo $test->myvar;		// prints as start

?>

 

why can't i change the base class variable?

[trq]

They are two completely different instances.

[optikalefx]

Ok i think i got it.  Once you make a variable in the parent class, its subclasses can't change it.

[jcbones]

Try:

$test->changeValue();
echo $test2->myvar . '<br />' . $test->myvar;

 

[KevinM1]

Ok i think i got it.  Once you make a variable in the parent class, its subclasses can't change it.

 

Nope, still wrong.  Try:

 

class Base
{
   protected $baseVar = "Start";

   public function show()
   {
      echo $this->baseVar;
   }
}

class Child extends Base
{
   public function edit($value)
   {
      $this->baseVar = $value; // Child has access to Base::baseVar because it inherits from Base
   }
}

$test = new Child();
$test->show(); // should display 'Start'
$test->edit("I'm changing my innards!  WEEEEE!");
$test->show();

[optikalefx]

I much better understand inheritance now.

 

My original thought was that the parent class had properties that all any sub class could change, as in the subclass is changing the parent's property.  But that is not inheritance.  That is just nonsense.  The parent class defines the variables that may exist in the subclass.  And every subclass has INSTANCES of the parent's properties, because the child class inherit those properties.

 

So if i have a a property in the parent class called $this->myvar.  Sub class 1 sets $this->myvar to "hello"  When subclass 2 gets instantiated, it is a NEW copy of the base class, and therefore the value of $this->myvar is not "hello" it is simply blank.  Upon changing $this->myvar in subclass 2, subclass 1 is STILL "hello"