B2Bbuilder php SQL inj

if (!empty($_GET["action"]))

$action=$_GET["action"];

else

$action="home";

//$action=empty($action)?"home":$_GET["action"];

//===============================

if(in_array($action, array('home','offer_cat','offer_list','offer_detail','product_cat','product_list','product_detail','news_cat','news_list','news_detail','corporate_cat','corporate_list','corporate_detail','search','corporate_moredetail','product_showimg')))

{

        require'inc/'.$action.'.php';

}

if(!empty($_GET['nid']))

{

        $nid=$_GET['nid'];

    $sql="select * from ".NEWSCAT." where pid=$nid";

    $db->query($sql);

    $sre=$db->getRows();

        if(count($sre)>0)

        {

                foreach($sre as $v)

                {

                        echo "[资讯]<a href='?action=news_list&newsid=".$v['catid']."'>".$v['cat']."</a><br/>";

                }

                echo "<br/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href='?action=news_cat'><i>返回</i></a><br/>";

                //echo "  <anchor>后退<prev/></anchor><br/>";

        }

        else

        {

                header("Location:./?action=news_list&nid=".$nid);

        exit();

        }

}

include_once("../module/".$_GET['m']."/includes/news_function.php");