이 오류가 왜 뜨고 어떻게 해결할 수 있는지 알려주세요.

<?php 
    include("C:/xampp/htdocs/include/lib.php");
    include("C:/xampp/htdocs/include/top.php");
?>

<?php $_SESSION['msg'] = ""; ?>
<?php 
    if($_POST){
        if(isset($_POST['in_date'])){

            $client = $_POST['client'];

            $product = $_POST['product'];

            $ea = $_POST['ea'];

            $in_date = $_POST['in_date'];

            if($client == "거래처선택"){$_SESSION['msg'] .= "거래처가 누락되었습니다. <br>";}
            if($product == "제품선택"){$_SESSION['msg'] .= "제품명이 누락되었습니다. <br>";}
            if(!$ea){$_SESSION['msg'] .= "제품개수가 누락되었습니다. <br>";}
            if(!$in_date){$_SESSION['msg'] .= "출고날짜가 누락되었습니다. <br>";}
            $re = sql("select * from stock where name='$product'");
            $da = fe($re);
            $ea_array = explode("/",$da['ea']);
            $price_array = explode("/" ,$da['price']);
            $date_array = explode("/", $da['date']);
            $ea_num = 0;
            for($i = 0; $i<count($ea_array); $i++){
                $ea_num += $ea_array[$i];
            }
            if($ea_num < $ea){$_SESSION['msg'] .= "제품개수가 잘못 입력되었습니다.";}

            if($_SESSION['msg'] == ""){

                $array = array();
              for($i = 0; $i<count($ea_array); $i++){
                $array = array("ea" => $ea_array[$i] , "price" => $price_array[$i] , "date" => $date_array[$i]);
              }

              array_multisort($array,array('date' => SORT_ASC));

              print_r($array);



                 /* sql("insert into out_pro(client,product,ea,in_price,out_pro,margin,totalprice,date) values('$client','$product',");*/ //out_pro에 넣으려고 했는데 보류
            }
        }else{

        }

    }
?>
        <div class="msg">
            <?php echo $_SESSION['msg']; ?>
        </div>
        <div class="title">출고관리</div>
    </div> 
</div>

<div id="con">

    <div class="wrap store">

    <form method = "post" action = "/page/out_pro.php">
        <div>   
            <span class="red">*</span> 거래처 : 
            <select name = "client">
                <option value="거래처선택">거래처선택</option>
                <?php 
                    $re = sql("select name from client order by name asc");
                    while($da = fe($re)){
                ?>
                <option value = "<?php echo $da['name']; ?>"><?php echo $da['name']; ?></option>
                <?php } ?>
            </select>
            &nbsp;&nbsp;&nbsp;&nbsp;

            <span class="red">*</span> 제품명 : 
            <select name = "product">
                <option value="제품선택">제품선택</option>
                <?php 
                    $re = sql("select * from product order by name asc");
                    while($da = fe($re)){
                ?>
                <option value = "<?php echo $da['name']; ?>"><?php echo $da['name']; ?></option>
                <?php } ?>
            </select>
            &nbsp;&nbsp;&nbsp;&nbsp;

            <span class="red">*</span> 제품개수 : <input name = "ea" type="text" style="width:70px;">
            &nbsp;&nbsp;&nbsp;&nbsp;

            <span class="red">*</span> 출고날짜 : <input type="text" name = "in_date" id="in_date" style="width:150px; text-align:center;">
              &nbsp;&nbsp;&nbsp;&nbsp;
            <input type = "submit" value = "출고하기">
        </div>
    </form>

        <div class="in_search">

            거래처 : 
            <select name = "client">
                <option value = "전 체">전 체</option>
                <?php 
                    $re = sql("select name from client order by name asc"); 
                    while($da = fe($re)){
                ?>
                <option value = "<?php echo $da['name']; ?>"><?php echo $da['name']; ?></option>
                <?php } ?>
            </select>

            &nbsp;&nbsp;&nbsp;&nbsp;

            제품별 : 
            <select name = "product">
                <option value = "전 체">전 체</option>
                <?php 
                    $re = sql("select * from product order by name asc");
                    while($da = fe($re)){
                ?>
                <option value = "<?php echo $da['name']; ?>"><?php echo $da['name']; ?></option>
                <?php } ?>
            </select>

             &nbsp;&nbsp;&nbsp;&nbsp;

             시작날짜 : <input type="text" name = "s_date" id="s_date" style="width:150px; text-align:center;">

             &nbsp;&nbsp;&nbsp;&nbsp;

             마지막날짜 : <input type="text" name = "e_date" id="e_date" style="width:150px; text-align:center;">

             &nbsp;&nbsp;&nbsp;&nbsp;
             <button>검색하기</button>     
        </div>
        <div class="s_list" >

            <div class="se_re">
                "거래처 : <span class="red"></span>", &nbsp; "제품명 : <span class="red"></span>", &nbsp; 
                "시작날짜 : <span class="red">이상</span>",   &nbsp;  "마지막날짜 : <span class="red"> 이하</span>" 
            </div>
            <div class="se_re2"> 
                총 <span class="red"></span> 건, 전체마진 <span class="red"></span> 원,
                전체출고총액 : <span class="red"></span> 원
            </div>

            <table class="list mat40">
                <tr>
                    <th>거래처</th>
                    <th>제품명</th>
                    <th>출고개수(총개수)</th>
                    <th>입고가</th>
                    <th>출고가</th>
                    <th>마 진</th>
                    <th>출고총액</th>
                    <th>출고날짜</th>

                </tr>

                <tr>
                    <td>-</td>
                    <td>-</td>
                    <td>-</td>
                    <td>-</td>
                    <td>-</td>
                    <td>-</td>
                    <td>-</td>
                    <td>-</td>
                </tr> 
            </table>

            <div class="w100 ac mat20">

                <button>이전</button>

                <button>1</button>

                <button>다음</button>

            </div>

        </div>
    </div>
</div>

</body>
</html>

DB구조 입니다.

product

stock

stock의 데이터들

아 참고로 product테이블의 no필드와 stock테이블의 idx는 autoincrease입니다.