배열로 받은 post 값 DB 저장 채택완료

write_skin.php에서

<tr>
  </tr>
      <td>
         <input name="wr_4[]" type="checkbox" id="wr_4" value="스카이"/>스카이</input>
      <input name="wr_4[]" type="checkbox" id="wr_4" value="지게차"/>지게차</input>
      <input name="wr_4[]" type="checkbox" id="wr_4" value="덤프사다리차"/>덤프사다리차</input> 
      </td>
  </tr>​

배열로 입력받고 post로 넘겨줬고요

write_update.php 부분에서

for($i=0 ; $i<sizeof($_POST[wr_4]) ; $i++){
     $wr_4 = $_POST[wr_4][$i];
 
 }

    $sql = " insert into $write_table
                set wr_num = '$wr_num',
                     wr_reply = '$wr_reply',
                     wr_comment = 0,
                     ca_name = '$ca_name',
                     wr_option = '$html,$secret,$mail',
                     wr_subject = '$wr_subject',
                     wr_content = '$wr_content',
                     wr_link1 = '$wr_link1',
                     wr_link2 = '$wr_link2',
                     wr_link1_hit = 0,
                     wr_link2_hit = 0,
                     wr_hit = 0,
                     wr_good = 0,
                     wr_nogood = 0,
                     mb_id = '{$member['mb_id']}',
                     wr_password = '$wr_password',
                     wr_name = '$wr_name',
                     wr_email = '$wr_email',
                     wr_homepage = '$wr_homepage',
                     wr_datetime = '".G5_TIME_YMDHIS."',
                     wr_last = '".G5_TIME_YMDHIS."',
                     wr_ip = '{$_SERVER['REMOTE_ADDR']}',
                     wr_1 = '$wr_1',
                     wr_2 = '$wr_2',
                     wr_3 = '$wr_3',
                     wr_4 = '$wr_4',
                     wr_5 = '$wr_5',
                     wr_6 = '$wr_6',
                     wr_7 = '$wr_7',
                     wr_8 = '$wr_8',
                     wr_9 = '$wr_9',
                     wr_10 = '$wr_10' ";
    sql_query($sql);​

이렇게 해서 인서트 해줬는데 실제로 값을 보면 A라는 글짜만 나오는데 왜 그런가요?