OOP in wordpress plugins – avoid multiple instances???

Hi,

I’m trying to add some OOP with php5 to my wordpress plugin..

so i have my class

class Test {
function __construct()
{
log("constructed");
}
}

$instance = new Test();

now when i test it in wordpress.. it always get 2 instances.. because my log shows “constructed” twice!

I tried avoiding it by an isset($instance) … but that didn’t work..

How can I avoid this, any help???

Thanks in advance!!