Show composition/aggregation/association relations between objects in Visual Paradigm UML diagrams?

Question

I have Netbeans installed with Visual Paradigm plugin.

I have converted my php code into UML diagrams (modeling -> instant reverse). I can see relations (drawn lines) between superclass and subclasses. However, i cannot see relations between objects inside objects (composition/aggregation/association)?

The code looks like:

class Thread {
    private $tag = '';

    public function __construct($tagObject) {
         $this->tag = $tagObject;
    }
}

I know its possible using Java cause i've read about it.

Im using PHP, is this still possible?