Question

I’ve been trying to self-teach some OOP lately, and I came across something which seems curiously strange to me. I was wondering if someone can explain this to me.

I was inspired by one of the questions on this site to try out this little test piece of code (in PHP):

class test1 {
    function foo ($x = 2, $y = 3) {
    return new test2($x, $y);
    }
}

class test2 {
    public $foo;
    public $bar;
    function __construct ($x, $y) {
        $foo = $x;
        $bar = $y;
    }
    function bar () {
        echo $foo, $bar;
    }
}

$test1 = new test1;
$test2 = $test1->foo('4', '16');
var_dump($test2);
$test2->bar();

Simple stuff. $test1 should return back an object to $test2, with $test2->foo equal to 4 and $test2->bar equal to 16. My problem with this is that, while $test2 is being made into an object of class test2, both $foo and $bar within $test2 are NULL. The constructor function is definitely being run – if I echo $foo and $bar in the constructor function, they show up (with the right values, no less). Yet, despite them being assigned values by $test1->foo, they don’t show up either through the var_dump or through $test2->bar. Can someone explain this bit of intellectual curiosity to me?

Answer 1

Your syntax is wrong, it should be:

class test2 {
    public $foo;
    public $bar;
    function __construct ($x, $y) {
        $this->foo = $x;
        $this->bar = $y;
    }
    function bar () {
        echo $this->foo, $this->bar;
    }
}