public function createGif()
    {
        $data = array();
        foreach ($this->data as $key => $item) {
            if ($item !== null) {
                $data[$key] = $item;
            }
        }
        return $this->tracking = self::GA_URL . '?' . http_build_query($data);
    }
public function createGif()
    {
        $data = array();
        foreach ($this->data as $key => $item) {
            if ($item !== null) {
                $data[$key] = $item;
            }
        }
        return $this->tracking = self::GA_URL . '?' . http_build_query($data);
    }
public function createGif ( ) { $ data = array ( ) ; foreach ( $ this -> data as $ key => $ item ) { if ( $ item !== null ) { $ data [ $ key ] = $ item ; } } return $ this -> tracking = self :: GA_URL . '?' . http_build_query ( $ data ) ; }
Create the GA callback url, aka the gif

@return string
Create the GA callback url aka the gif