public static $allowed_actions = array (
   'search',
   'SearchForm'
);

public function SearchForm() {
      
   $fields = new FieldSet(
      new DropDownField('Type', array(
         'all' => 'All',
         'new' => 'New',
         'used' => 'Used'
      )),
      new TextField('Query','Query')
   );
      
   $actions = new FieldSet(
      new FormAction('doSearch', 'Search')
    );
      
   $form = new Form($this, 'SearchForm', $fields, $actions);
   
   return $form;
   
}

public function doSearch($data, $form) {
      
   $Query = urlencode($data['Query']);
      
   $Type = $data['Type'];

   if ($Type && $Query) Director::redirect($this->Link("search/$Type/$Query")); // Redirect to a search result page i.e. "www.site.com/camcorders/search/used/sony+HD+bargain" you'll probably want to tweak how this part redirects if you're going to have the search form on every page i.e. don't use $this->Link

}

public function SearchResults() {
      
   $Params = $this->getURLParams();

   $Action = $Params['Action'];

   $Type = $Params['ID'];

   $Query = Convert::raw2sql(urldecode($Params['OtherID']));

   if (Action == 'search' && $SearchQuery && $Type){
      
      $where ="Title LIKE '%$Query%' OR Description LIKE '%$Query%'";
      $sort ='';
      $join='';
      $error=false;
      
      switch ($Type) {
         case 'all':
            break;
         case 'new':
            $where.= " && TypeID = 1";
            break;
         case 'used':
            $where.= " && TypeID = 2";
            break;
         default:
            $error = true;
            break;
      }
      
      if ($error) return $this->httpError(404);
      
      return DataObject::get('Camcorder', "".$where, $sort, $join);
      
   }

}