public function campaign()
    {
        if ($this->campaign === null) {
            $this->campaign = $this->generateCampaign();
        }

        return $this->campaign;
    }
public function campaign()
    {
        if ($this->campaign === null) {
            $this->campaign = $this->generateCampaign();
        }

        return $this->campaign;
    }
public function campaign ( ) { if ( $ this -> campaign === null ) { $ this -> campaign = $ this -> generateCampaign ( ) ; } return $ this -> campaign ; }
Get the campaign identifier.

If it has not been explicitely set, it will be auto-generated (with uniqid).

@return string
Get the campaign identifier .