function DetectSymbianOS()
   {
       if (stripos($this->useragent, $this->deviceSymbian) > -1 || 
           stripos($this->useragent, $this->deviceS60) > -1 ||
           stripos($this->useragent, $this->deviceS70) > -1 || 
           stripos($this->useragent, $this->deviceS80) > -1 ||
           stripos($this->useragent, $this->deviceS90) > -1)
         return $this->true; 
      else
         return $this->false; 
   }