Question:What is the output of the following script?
<?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();
?>
 
A  
B  
C  
D  
E a: 10, b: 10