为什么无法使用php中mysqli的准备语句进行数据库中数据的查询（绑定参数或者绑定结果），项目急用！该如何处理

stmt_init();
    //为执行准备语句
    $stmt->prepare($query);
    //执行语句
    $stmt->execute();
    //绑定结果参数
    $stmt->bind_result($name,$pwd);
    //循环处理结果并

function selectLink($oid){
        $sql = "select o.oid,l.lid,c.cid,comName,comPrice,ordTime
                from mis_order o,mis_link l,mis_commodity c
                where o.oid=l.lid and c.cid=l.cid and o.oid=?";
        $stmt = $this->mysqli->prepare($sql);
        $stmt->bind_param("i",$oid);
        $stmt->execute();
        $stmt->store_result();
        $stmt->bind_result($oid,$lid,$cid,$comName,$comPrice,$ordTime);
        $rows = $stmt->affected_rows;
        if($rows > 0){
            $arrLink = array();
            while($stmt->fetch()){
                 $arr = array(
                    "oid" => $oid,
                    "lid" => $lid,
                    "cid" => $cid,
                    "comName" => $comName,
                    "comPrice" => $comPrice,
                    "ordTime" => $ordTime
                );
                array_push($arrLink,$arr);
            }
            return $arrLink;
        }else{
            echo "查询订单明细失败!
";
        }
    }