Avoiding if-statements with object oriented design, PHP

I'm basically creating a display-module for an ad-system I've created.

I'm trying to avoid the following construction, with repeated if-statements.

My gut feeling tells me there's a smarter way to do this, maybe with polymorphism?

<?php

class Ad { 
    public $adState = 'active'; 
} 

class AdWriter { 
    public function displayAd(Ad $ad, $viewmode = 'visitor') { 
        if ($viewmode =='visitor') { 
            if ($adState == 'active') {} 

            else if ($adState == 'paused') {} 

            else if ($adState == 'inactive') {} 

        } 

        else if ($viewmode = 'owner') { 
            if ($adState == 'active') {} 

            else if ($adState == 'paused') {} 

            else if ($adState == 'inactive') {} 
        } 

        else if ($viewmode == 'administrator') { 
            if ($adState == 'active') {} 

            else if ($adState == 'paused') {} 

            else if ($adState == 'inactive') {} 
        } 
    } 
}  

?>