<tr>
  <th>クーポン</th>
     <td colspan="3">
     <!--{assign var=key value="search_order_coupon"}-->
       <span class="attention"><!--{$arrErr[$key]}--></span>
       <!--{html_radios name="$key" options=$arrCouponUseFlag selected=$arrForm[$key].value}-->
     </td>
   </tr>

function init()
    {
        parent::init();
        // クーポン割引プラグイン
        $this->arrCouponUseFlag = array(
           0 => '未使用',
           1 => '使用'
           );
    }


   public function lfInitParam(&$objFormParam)
    {
      $objFormParam->addParam('注文番号1', 'search_order_id1', INT_LEN, 'n', array('MAX_LENGTH_CHECK', 'NUM_CHECK'));
      $objFormParam->addParam('注文番号2', 'search_order_id2', INT_LEN, 'n', array('MAX_LENGTH_CHECK', 'NUM_CHECK'));

      (中略)

      // クーポン
      $objFormParam->addParam('クーポン', 'search_order_coupon', INT_LEN, 'n', array('MAX_LENGTH_CHECK', 'NUM_CHECK'));
    }

    public function buildQuery($key, &$where, &$arrValues, &$objFormParam)
    {
        $dbFactory = SC_DB_DBFactory_Ex::getInstance();
        switch ($key) {
            case 'search_product_name':
                $where .= ' AND EXISTS (SELECT 1 FROM dtb_order_detail od WHERE od.order_id = dtb_order.order_id AND od.product_name LIKE ?)';
                $arrValues[] = sprintf('%%%s%%', $objFormParam->getValue($key));
                break;
        
         (中略）
         
            // クーポン
            case 'search_order_coupon':
                $where .= ' AND coupon_discount_price !=0';     ←ココ
                $arrValues[] = $objFormParam->getValue($key);
                break;
            default:
                break;
        }
     }

// クーポン
case 'search_order_coupon':
    $coupon_flg = $objFormParam->getValue($key);
    if ($coupon_flg == 1) {
        $where .= ' AND coupon_discount_price !=0';
    } elseif ($coupon_flg == 0) {
        $where .= ' AND coupon_discount_price =0';
    }
    $arrValues[] = $objFormParam->getValue($key);
    break;