value variable url get

<label><?php echo JText::_('SR_SEARCH_ROOMS') ?></label>
			  <select class="span12 " name="codice">
					
						<option value=""><?php echo JText::_('SR_SEARCH_TIPOLOGIA1') ?>
</option>
                        <option value="3"><?php echo JText::_('SR_SEARCH_TIPOLOGIA2') ?>
</option>
                        <option value="1"><?php echo JText::_('SR_SEARCH_TIPOLOGIA3') ?>
</option>
                        <option value="2"><?php echo JText::_('SR_SEARCH_TIPOLOGIA4') ?>
</option>
                         <option value="6"><?php echo JText::_('SR_SEARCH_TIPOLOGIA5') ?>
</option>
                         <option value="5"><?php echo JText::_('SR_SEARCH_TIPOLOGIA6') ?>
</option>
					
				</select>

protected function getListQuery()
    {
        $dbo = $this->getDbo();
        $query = $dbo->getQuery(true);
		$nullDate = $dbo->getNullDate();
		

        $query->select( $this->getState('list.select', 't.*, cgroup.name as customer_group_name' ));

        $query->from($dbo->quoteName('#__sr_tariffs').' AS t');

		$roomTypeId = $this->getState('filter.room_type_id', NULL);
		$codice = $this->getState('filter.codice', NULL);
		$codice = $_GET['codice'];
//$tariffa = $_POST['codice'];

		if (isset($roomTypeId))
		{
			$query->where('t.room_type_id = '.(int) $roomTypeId);
		
		$query->where("t.codice LIKE '%$codice%'");
		//echo $query;