What is the output of the following code?
class A {
public $a= 1;
public function _construct($a) { $this->a = $a; }
public function mul() {
}
return function($x) {
return $this->a*$x;
};
$a= new A(2);
$a->mul = function($x) {
return $x*$x;
};
$m = $a->mul();
echo $m(3);
A . 9
B . 6
C . 0
D . 3
Answer: B