체크박스 선택시 전부다 첫번째 벨류값만 출력

<tr>
                <th scope="row">학년선택</th>
                <td>
                <label><input type="checkbox" name="wr_2[]" value="1" <? if($write['wr_2'] == "1"){ echo 'checked'; } ?> class="wr_2"> 1</label>
                <label><input type="checkbox" name="wr_2[]" value="2" <? if($write['wr_2'] == "2"){ echo 'checked'; } ?> class="wr_2"> 2</label>
                <label><input type="checkbox" name="wr_2[]" value="3" <? if($write['wr_2'] == "3"){ echo 'checked'; } ?> class="wr_2"> 3</label>
                <label><input type="checkbox" name="wr_2[]" value="4" <? if($write['wr_2'] == "4"){ echo 'checked'; } ?> class="wr_2"> 4</label>
                <label><input type="checkbox" name="wr_2[]" value="5" <? if($write['wr_2'] == "5"){ echo 'checked'; } ?> class="wr_2"> 5</label>
                <label><input type="checkbox" name="wr_2[]" value="6" <? if($write['wr_2'] == "6"){ echo 'checked'; } ?> class="wr_2"> 6</label>
                
                
                <script>
                    var str_wr_2 = "<?=@$write['wr_2']?>";
                    $("input:checkbox[name='wr_2[]']").each(function(index){
                        if(str_wr_2.indexOf($(this).val()) > -1){
                            $(this).attr("checked", true);
                        }
                    });
                </script>
            </td>
        </tr>

<?

$wr_2 = @implode("|", $_POST['wr_2']);

 

$sql = " update $g5[write_prefix]$bo_table set wr_2 = '$wr_2' where wr_id = '$wr_id' ";
sql_query($sql);

?>