AddWhere

function AddWhere($str)
{
   global $where;
   if ($where) return $where." and $str ";
   else return $str;
}

    function AddWhere($str,$where='')
    {
//        global $where;
        if ($where) return $where." and $str ";
        else return $str;
    }

$where =$this->AddWhere("area = '南山区'",$where);