Why does this happen?

[ryy705]

Hello,

 

  I expected the following code to display a:40 b:10  but it displays  a: 30, b: 10.  It seems that only  $this->a is getting passed to  parent::changeValue() instead of  the sum of $this->a + $this->b.  Whys is that?

 

<?php

class ClassOne {
  protected $a = 10;

  public function changeValue($b) {
    $this->a = $b;
  }
}

class ClassTwo extends ClassOne {

  protected $b = 10;

  public function changeValue($b) {
    $this->b = 10;
    parent::changeValue($this->a + $this->b);
  }

  public function displayValues() {
    print "a: {$this->a}, b: {$this->b}\n";
  }
}

$obj = new ClassTwo();

$obj->changeValue(20);
$obj->changeValue(10);

$obj->displayValues();

[DyslexicDog]

 public function changeValue($b) {
    $this->b = 10;

you reset the value of $this->b to 10 every time you call that function. Pretty sure that's where your problem is.

[genericnumber1]

when you pass a value to changeValue($b) in the subclass, you don't actually do anything with it. Perhaps you meant to do $this->b = $b instead of 10?

[bogeyman]

Maybe you can try this. Change this line.

 

    parent::changeValue($this->a + $this->b);

 

To

 

    parent::changeValue($this->a + $b);